From willamette-fcst at listsmart.osl.state.or.us Wed Sep 1 08:32:49 2010 From: willamette-fcst at listsmart.osl.state.or.us (Willamette Valley Field Burning Forecast) Date: Wed, 1 Sep 2010 08:32:49 -0700 Subject: [willamette-fcst] Wed, Sep 1st, 2010 Message-ID: SILVERTON HILLS FIELD BURNING FORECAST OREGON DEPARTMENT OF FORESTRY WEATHER OFFICE 9:00 AM PDT WED SEP 01 2010 BURN ADVISORY: Recommended burn times for agricultural burning are from 8:00am to 4:00pm. Prep burning is not allowed. Propane flaming is not allowed. WEATHER DISCUSSION: A weakening Pacific cold front is moving through the region this morning. Valley rainfall totals have generally been less than a tenth of an inch, but mountain locations have received considerably more rain. Log Creek, near Mt Hood picked up over 2.5 inches in the past 24 hours. Closer to home, Horse Creek, in the Cascade foothills picked up .19 and Yellowstone Mountain recorded .62 inches. Silverton had .04 in the rain guage, Jordan Valley recorded .12 and Turner picked up .01 during the past 24 hours. Upper air charts show a ridge of high pressure aloft beginning to build off the Oregon/Washington coast. This ridge will help to gradually decrease precipitation during the day today. However skies should remain mostly cloudy and relative humidities quite high for little drying of fields this afternoon. The ODF morning surface analysis showed the remains of the weak front trailing southwestward from a minor surface low near Astoria. There is a well developed thermal trough in California but it does not extend into Oregon. Gradients are generally southerly and forecast models show a light southerly transport wind today. For the mid Willamette Valley expect some light showers through the morning hours, then mostly cloudy skies this afternoon. Salem's high temperature today will be near 69, minimum relative humidity 59%. Sunset tonight: 7:43 pm THREE-HOURLY DATA: 11am 2pm 5pm 8pm Temperature: 63 67 69 65 Relative Humidity: 81% 70% 59% 68% Surface Wind Direction: 190 220 210 350 Surface Wind Speed: 9 5 6 6 Transport Wind Direction: 210 200 190 180 Transport Wind Speed: 5 6 6 5 Estimated Mixing Height: 1000 2500 2900 1000 Ventilation Index: 5 15 17 5 EXTENDED DISCUSSION: Today marks the final surge of moisture into the Pacific Northwest for the next couple of days. High pressure will quickly build offshore tonight and shift inland later tomorrow for a quick warm-up. Temperatures tomorrow will jump on the order of 15 degrees compared to today. At this point it appears that transport wind directions will be unfavorable for burning Thursday and Friday. By late Friday the ridge over the region begins to shift east as another upper level trough approaches from the Pacific. This should bring cooler weather to the mid Willamette valley once again this weekend, although not as cool as the past couple of days. There is a potential for some light rain over the weekend, but moisture appears quite limited. Longer range models indicate a second trough aproaching early next week. EXTENDED FORECAST: Thursday: Morning low clouds or fog, otherwisesunny. 85. N 5-10 mph. Friday: Sunny, with a high near 87. N 5-10 g 15 mph. Saturday: Partly sunny, with a high near 78. Sunday: Partly sunny, with a high near 75. Monday: Partly sunny, with a high near 75. Tuesday: Partly sunny, with a high near 74. Notes: 1. Mixing height, as used here, is the lowest height at which the potential temperature exceeds the potential temperature at the surface. As a practical matter it is the approximate height to which a smoke plume will rise assuming good ignition, dry fuels, and winds less than about 15mph. 2. Transport winds are a layer average through the mixing height, weighted slightly toward the winds at the top of the layer. 3. Ventilation Index is the height of the mixing layer times the transport wind speed divided by 1000. 4. Surface wind direction is the general expected wind direction. At a specific point surface winds are highly dependent on local terrain conditions. This forecast is provided under an agreement between the Oregon Department of Agriculture and the Oregon Department of Forestry. For information contact ODA at 503-986-4701. -------------- next part -------------- An HTML attachment was scrubbed... URL: From willamette-fcst at listsmart.osl.state.or.us Wed Sep 1 11:46:01 2010 From: willamette-fcst at listsmart.osl.state.or.us (Willamette Valley Field Burning Forecast) Date: Wed, 1 Sep 2010 11:46:01 -0700 Subject: [willamette-fcst] Wed, 1 Sep 2010 Message-ID: SILVERTON HILLS FIELD BURNING FORECAST OREGON DEPARTMENT OF FORESTRY WEATHER OFFICE 12:00 PM PDT WED SEP 01 2010 BURN ADVISORY: Recommended burn times for agricultural burning are from now until 4:00pm. Prep burning is not allowed. Propane flaming is not allowed. WEATHER DISCUSSION: Satellite pictures show the thickest clouds have now moved into the southern Willameete Valley as of late morning. Some breaks in the clouds are showing up over the northern coast range and southward into Polk and Marion counties. Temperatures are running 5 or 6 degrees warmer than yesterday at the same time across the northern Willamette Valley. The late morning ODF surface analysis show higher pressure beginning to build off the Washington coast, but surface wind directions is still southerly at most valley locations. Surface winds will eventually shift to northerly but right now that looks like it won't happen until this evening. The morning Salem sounding showed warming from the surface to above 14,000 feet and with warmer air aloft, even with surface heating, mixing heights will be suppressed today. Best estimate is maximum mixing heights not quite reaching 3000 feet. With low mixing heights and an unfavorable southerly wind direction through the afternoon conditions do not look favorable for open field burning today. For the mid Willamette Valley expect partly to mostly cloudy skies this afternoon. Salem's high temperature today will be near 73, minimum relative humidity 53%. Sunset tonight: 7:43 pm THREE-HOURLY DATA: 2pm 5pm 8pm Temperature: 71 73 66 Relative Humidity: 61% 53% 63% Surface Wind Direction: 200 140 350 Surface Wind Speed: 6 4 5 Transport Wind Direction: 200 190 250 Transport Wind Speed: 6 6 5 Estimated Mixing Height: 2500 2900 1000 Ventilation Index: 15 17 5 EXTENDED DISCUSSION: *** Latest computer models now suggest a possible *** *** burn opportunity Friday afternoon. *** This morning was the final surge of moisture into the Pacific Northwest for the next couple of days. High pressure will quickly build offshore tonight and shift inland later tomorrow for a quick warm-up. Temperatures tomorrow will jump on the order of 15 degrees compared to today. At this point it appears that transport wind directions will be northerly and thus unfavorable for burning Thursday. By late Friday the ridge over the region begins to shift east as another upper level trough approaches from the Pacific. This should bring cooler weather to the mid Willamette valley once again this weekend, although not as cool as the past couple of days. Latest computer models are suggesting a marine push ahead of the trough Friday afternoon for a possible burn opportunity. This is a change from earlier forecasts. There is a potential for some light rain over the weekend, but moisture appears quite limited. Longer range models indicate a second trough aproaching early next week. EXTENDED FORECAST: Thursday: Morning low clouds or fog, otherwisesunny. 85. N 5-10 mph. Friday: Sunny, with a high near 87. N 5-10 g 15 mph becomming westerly in the afternoon. Saturday: Partly sunny, with a high near 78. Sunday: Partly sunny, with a high near 75. Monday: Partly sunny, with a high near 75. Tuesday: Partly sunny, with a high near 74. Notes: 1. Mixing height, as used here, is the lowest height at which the potential temperature exceeds the potential temperature at the surface. As a practical matter it is the approximate height to which a smoke plume will rise assuming good ignition, dry fuels, and winds less than about 15mph. 2. Transport winds are a layer average through the mixing height, weighted slightly toward the winds at the top of the layer. 3. Ventilation Index is the height of the mixing layer times the transport wind speed divided by 1000. 4. Surface wind direction is the general expected wind direction. At a specific point surface winds are highly dependent on local terrain conditions. This forecast is provided under an agreement between the Oregon Department of Agriculture and the Oregon Department of Forestry. For information contact ODA at 503-986-4701. -------------- next part -------------- An HTML attachment was scrubbed... URL: From willamette-fcst at listsmart.osl.state.or.us Thu Sep 2 10:15:41 2010 From: willamette-fcst at listsmart.osl.state.or.us (Willamette Valley Field Burning Forecast) Date: Thu, 2 Sep 2010 10:15:41 -0700 Subject: [willamette-fcst] Thu, 02 September 2010 Message-ID: SILVERTON HILLS FIELD BURNING FORECAST OREGON DEPARTMENT OF FORESTRY WEATHER OFFICE 9:00 AM PDT THU SEP 02 2010 BURN ADVISORY: Recommended burn times for agricultural burning are from 10:00am to 4:00pm. Prep burning is allowed from 2:00pm to 5:00pm with a 50 acre limit. Propane flaming is allowed from 2:00pm to 5:00pm. WEATHER DISCUSSION: Temperatures should top out 10-12 degrees warmer today than yesterday. The morning Salem sounding showed the warming nicely. It was warmer than yesterday morning at all elevations above about 1700 feet. At 5000 feet the temperature had jumped from 46 degrees yesterday to 62F this morning. Two distinct inversions showed up on the sounding, one from 1300 to 1800 feet and another from 2500 to 3400 feet. Models show additional warming aloft for today. None the less, with mostly sunny skies today surface heating should push surface temperatures into the upper 80's which will help push mixing heights to above 3000 feet this afternoon. The morning ODF surface analysis shows a well developed thermal trough extending from California's central Valley to near Cape Blanco, then right along the Oregon Coast to about Astoria. The thermal trough will shift inland today and be over the Willamette Valley by late afternoon. Weak surface high pressure is located just west of northwest Washington. With higher pressure to the north and lower pressure with the thermal trough moving into the Willamette Valley transport winds will be generally northerly or north-northeasterly this afternoon. This is an unfavorable wind direction for open field burning. Upper air charts show a ridge from California to northwest Canada and a trough in the Gulf of Alaska. Both of these features are moving steadily eastward today with the trough axis forecast to be about 400 miles west of Vancouver Island by this evening. For the mid Willamette Valley today, expect any clouds this morning to quickly dissipate and nearly full sunshine this afternoon. The sun, and the dry north-northeast winds should help dry fields from recent rains. Salem's high temperature today will be near 87. Relative humidity drops to 50% by 11am. Minimum relative humidity 27%. Sunset tonight: 7:41 pm THREE-HOURLY DATA: 11am 2pm 5pm 8pm Temperature: 68 81 87 80 Relative Humidity: 59% 35% 27% 36% Surface Wind Direction: 020 020 020 020 Surface Wind Speed: 8 12 12 5 Transport Wind Direction: 020 040 030 360 Transport Wind Speed: 8 9 11 9 Estimated Mixing Height: 2000 2900 3400 5000 Ventilation Index: 16 26 37 45 EXTENDED DISCUSSION: The trough in the Gulf of Alaska will help kick the thermal trough east of the Cascades on Friday opening up the door for westerly transport flow over the region. Timing is the key, but at this point it looks like westerly winds will develop by early afternoon and this could develop into a good burn opportunity. An active weather pattern is on tap for the Saturday and into the first part of next week. A relative quick moving upper level trough will swing down from the Gulf of Alaska and over the Pacific Northwest beginning late Saturday and move east of the Rockies by early Monday. This will keep cooler temperatures across the region for the Labor Day weekend with periodic showers. Models indicate only a short break before another trough swings down from Alaska early Tuesday. EXTENDED FORECAST: Friday: Sunny, with a high near 87. Wind becoming west 7-10 mph. Saturday: Partly sunny, but a chance of light showers. 77. SSW 5-8 becoming NNW. Sunday: Partly sunny, but a chance of light showers. 75. Monday: Partly sunny, with a high near 75. Tuesday: Mostly cloudy periods of rain, 74. Wednesday: Partly sunny, with a high near 73. Notes: 1. Mixing height, as used here, is the lowest height at which the potential temperature exceeds the potential temperature at the surface. As a practical matter it is the approximate height to which a smoke plume will rise assuming good ignition, dry fuels, and winds less than about 15mph. 2. Transport winds are a layer average through the mixing height, weighted slightly toward the winds at the top of the layer. 3. Ventilation Index is the height of the mixing layer times the transport wind speed divided by 1000. 4. Surface wind direction is the general expected wind direction. At a specific point surface winds are highly dependent on local terrain conditions. This forecast is provided under an agreement between the Oregon Department of Agriculture and the Oregon Department of Forestry. For information contact ODA at 503-986-4701. -------------- next part -------------- An HTML attachment was scrubbed... URL: From willamette-fcst at listsmart.osl.state.or.us Thu Sep 2 11:33:59 2010 From: willamette-fcst at listsmart.osl.state.or.us (Willamette Valley Field Burning Forecast) Date: Thu, 2 Sep 2010 11:33:59 -0700 Subject: [willamette-fcst] Thu, 02 Sep 10 Message-ID: SILVERTON HILLS FIELD BURNING FORECAST OREGON DEPARTMENT OF FORESTRY WEATHER OFFICE 12:00 PM PDT THU SEP 02 2010 BURN ADVISORY: Recommended burn times for agricultural burning are from 10:00am to 4:00pm. Prep burning is allowed from 2:00pm to 5:00pm with a 50 acre limit. Propane flaming is allowed from 2:00pm to 5:00pm. WEATHER DISCUSSION: Temperatures are on track to reach the mid 80's this afternoon. The late morning ODF surface analysis shows that a well developed thermal trough remains from California's central Valley to near Cape Blanco, then right along the Oregon Coast to about Astoria. The thermal trough will shift inland later today and be over the Willamette Valley by late afternoon. Transport winds will be generally northerly or north-northeasterly this afternoon. This is an unfavorable wind direction for open field burning. Upper air charts show a ridge from Nevada to northwest Canada and a trough in the Gulf of Alaska. Both of these features are moving steadily eastward today with the trough axis forecast to be about 400 miles west of Vancouver Island by this evening. For the mid Willamette Valley today, any cloudiness still left will dissipate for nearly full sunshine this afternoon. The sun, and the dry north-northeast winds should help dry fields from recent rains. Salem's high temperature today will be near 87. Minimum relative humidity this afternoon will dip to 27%. Sunset tonight: 7:41 pm THREE-HOURLY DATA: 11am 2pm 5pm 8pm Temperature: 68 81 87 80 Relative Humidity: 59% 35% 27% 36% Surface Wind Direction: 020 020 020 020 Surface Wind Speed: 8 12 12 5 Transport Wind Direction: 020 040 030 360 Transport Wind Speed: 8 9 11 9 Estimated Mixing Height: 2000 2900 3400 5000 Ventilation Index: 16 26 37 45 EXTENDED DISCUSSION: The trough in the Gulf of Alaska will help kick the thermal trough east of the Cascades on Friday opening up the door for northwesterly transport flow over the region. Timing is the key, but at this point it looks like northwesterly winds will develop by early to mid-afternoon and this could develop into a good burn opportunity. Models indicate mixing heights reaching 3000 feet by mid-afternoon as well. An active weather pattern remains on tap for the Saturday and into the first part of next week. A relative quick moving upper level trough will swing down from the Gulf of Alaska and over the Pacific Northwest beginning late Saturday and move east of the Rockies by early Monday. This will keep cooler temperatures across the region for the Labor Day weekend with periodic showers. Models indicate only a short break before another trough swings down from Alaska early Tuesday. EXTENDED FORECAST: Friday: Sunny, with a high near 87. Wind becoming west 7-10 mph. Saturday: Partly sunny, but a chance of light showers. 77. SSW 5-8 becoming NNW. Sunday: Partly sunny, but a chance of light showers. 75. Monday: Partly sunny, with a high near 75. Tuesday: Mostly cloudy periods of rain, 74. Wednesday: Partly sunny, with a high near 73. Notes: 1. Mixing height, as used here, is the lowest height at which the potential temperature exceeds the potential temperature at the surface. As a practical matter it is the approximate height to which a smoke plume will rise assuming good ignition, dry fuels, and winds less than about 15mph. 2. Transport winds are a layer average through the mixing height, weighted slightly toward the winds at the top of the layer. 3. Ventilation Index is the height of the mixing layer times the transport wind speed divided by 1000. 4. Surface wind direction is the general expected wind direction. At a specific point surface winds are highly dependent on local terrain conditions. This forecast is provided under an agreement between the Oregon Department of Agriculture and the Oregon Department of Forestry. For information contact ODA at 503-986-4701. -------------- next part -------------- An HTML attachment was scrubbed... URL: From willamette-fcst at listsmart.osl.state.or.us Fri Sep 3 08:45:41 2010 From: willamette-fcst at listsmart.osl.state.or.us (Willamette Valley Field Burning Forecast) Date: Fri, 3 Sep 2010 08:45:41 -0700 Subject: [willamette-fcst] September 3 Message-ID: SILVERTON HILLS FIELD BURNING FORECAST OREGON DEPARTMENT OF FORESTRY WEATHER OFFICE 9:00 AM PDT FRI SEP 03 2010 BURN ADVISORY: Agricultural burning burning is not recommended. Prep burning is allowed from 12:30pm to 5:00pm with a 50 acre limit. Propane flaming is allowed from 12:30pm to 5:00pm. WEATHER DISCUSSION: Upper level ridge has moved off to the east with the upper trough moving in this morning. Surface pressure pattern shows the thermal trough in the Willamette Valley this morning. The Newport to Salem gradient is .9 mb onshore while the Salem to Redmond gradient is 3.6 mb offshore. As the upper level trough continues marching in today, onshore pressure gradients will increase as the surface thermal trough shifts east of the Cascades late this morning to early afternoon. This will set up a decent marine push this afternoon. The morning sounding from Salem showed a strong surface and subsidence inversion to nearly 4000 ft, which demonstrates the remaining strength of the exiting upper level ridge. Winds up to 1500 ft are generally light and variable but show a distinct light SW'erly flow above. Weather conditions for today will again be mostly sunny with the high temperature a little cooler than yesterday's high of 90. Expect the temperature to top out around 85 a little earlier this afternoon as the cooler marine air starts pushing into the region. Mixing heights will remain fairly low this morning but as cooler air moves in aloft this afternoon combined with surface heating, mixing will rapidly improve during the early afternoon. Relative humidity will drop below 50 percent by 11 a.m. with the minimum humidity nearly 32 percent. SW'erly flow aloft will continue and increase today with westerly surface winds starting to show up in the valley by early to mid afternoon. All indications point to a good burning opportunity today. Sunset tonight: 7:40 pm THREE-HOURLY DATA: 11am 2pm 5pm 8pm Temperature: 75 82 84 73 Relative Humidity: 48% 37% 33% 49% Surface Wind Direction: 230 270 270 290 Surface Wind Speed: 4 5 10 8 Transport Wind Direction: 220 240 260 290 Transport Wind Speed: 7 10 12 10 Estimated Mixing Height: 1800 4200 5000 1500 Ventilation Index: 13 42 60 15 EXTENDED DISCUSSION: Upper level trough moves into the state on Saturday ushering in much cooler conditions. Expect mostly cloudy skies with breezy onshore, NW'erly winds during the afternoon. Mixing will be good but the more gradient stacking will be to the east. Trough moves off to the east Sunday with a minor ridge building in. This will be very temporary as another trough forms in the eastern Pacific Monday and moves in Monday night. This trough will likely be a little stronger and bring some light rain to the region on Tuesday. Trough exits to the east Wednesday. Overall, expect a considerably cooler, fall-like air mass over the region over the weekend and into next week. EXTENDED FORECAST: Saturday: Partly sunny, with a high near 72. Northwest wind between 5 and 10 mph. Saturday Night: A 30 percent chance of showers after 11pm. Mostly cloudy, with a low around 46. North northwest wind between 5 and 8 mph becoming calm. Sunday: A 30 percent chance of showers before 11am. Partly sunny, with a high near 68. Southwest wind 5 to 7 mph becoming west northwest. Sunday Night: Mostly cloudy, with a low around 47. Monday: Mostly cloudy, with a high near 72. Monday Night: Mostly cloudy, with a low around 48. Tuesday: Mostly cloudy with occasional light rain, with a high near 67. Tuesday Night: Mostly cloudy with occasional light rain, with a low around 48. Wednesday: Mostly cloudy early then partly sunny, with a high near 70. Wednesday Night: Mostly cloudy, with a low around 50. Thursday: Partly sunny, with a high near 72. Notes: 1. Mixing height, as used here, is the lowest height at which the potential temperature exceeds the potential temperature at the surface. As a practical matter it is the approximate height to which a smoke plume will rise assuming good ignition, dry fuels, and winds less than about 15mph. 2. Transport winds are a layer average through the mixing height, weighted slightly toward the winds at the top of the layer. 3. Ventilation Index is the height of the mixing layer times the transport wind speed divided by 1000. 4. Surface wind direction is the general expected wind direction. At a specific point surface winds are highly dependent on local terrain conditions. This forecast is provided under an agreement between the Oregon Department of Agriculture and the Oregon Department of Forestry. For information contact ODA at 503-986-4701. -------------- next part -------------- An HTML attachment was scrubbed... URL: From willamette-fcst at listsmart.osl.state.or.us Fri Sep 3 11:46:47 2010 From: willamette-fcst at listsmart.osl.state.or.us (Willamette Valley Field Burning Forecast) Date: Fri, 3 Sep 2010 11:46:47 -0700 Subject: [willamette-fcst] August 27 Message-ID: SILVERTON HILLS FIELD BURNING FORECAST OREGON DEPARTMENT OF FORESTRY WEATHER OFFICE 12:00 PM PDT FRI SEP 03 2010 BURN ADVISORY: Agricultural burning burning is not recommended. Prep burning is not allowed. Propane flaming is allowed from 12:30pm to 5:00pm. WEATHER DISCUSSION: Upper level ridge has moved off to the east with the upper trough moving in. Surface pressure pattern shows the thermal trough in the Willamette Valley but shifting to the east side of the Valley. The Newport to Salem gradient has increased to 2.3 mb onshore with the Salem to Redmond gradient lowering to 1.6 mb offshore. As the upper level trough continues marching in today, onshore pressure gradients will increase as the surface thermal trough shifts east of the Cascades by early afternoon. This will set up a decent marine push. The morning sounding from Salem showed a strong surface and subsidence inversion to nearly 4000 ft. Surface heating has only allowed the mixing to rise to near 1500 ft. around 11 a.m. Winds from the Salem SODAR are showing SSW to W winds aloft at 5 - 10 mph. Weather conditions for today will again be mostly sunny with the high temperature a little cooler than yesterday's high of 90. Expect the temperature to top out around 85 a little earlier this afternoon as the cooler marine air starts pushing into the region. Mixing heights will remain fairly low this morning but as cooler air moves in aloft this afternoon combined with surface heating, mixing will rapidly improve during the early afternoon. Relative humidity has dropped below 50 percent with the minimum humidity expected near 30 percent. SW'erly flow aloft will continue to increase today with light south to west surface winds starting to show up in the Valley. All indications point to a good burning opportunity today. Sunset tonight: 7:40 pm THREE-HOURLY DATA: 2pm 5pm 8pm Temperature: 85 84 73 Relative Humidity: 32% 35% 55% Surface Wind Direction: 270 270 290 Surface Wind Speed: 7 12 9 Transport Wind Direction: 240 260 290 Transport Wind Speed: 10 14 10 Estimated Mixing Height: 4200 5000 1500 Ventilation Index: 42 60 15 EXTENDED DISCUSSION: Upper level trough moves into the state on Saturday ushering in much cooler conditions. Expect mostly cloudy skies with breezy onshore, NW'erly winds during the afternoon. Mixing will be good but more gradient stacking will be to the east. Trough moves off to the east Sunday with a minor ridge building in. This will be very temporary as another trough forms in the eastern Pacific Monday and moves in Monday night. This trough will likely be a little stronger and bring some light rain to the region on Tuesday. Trough exits to the east Wednesday. Overall, expect a considerably cooler, fall-like air mass over the region over the weekend and into next week. EXTENDED FORECAST: Saturday: Partly sunny, with a high near 72. Northwest wind between 5 and 10 mph. Saturday Night: Mostly cloudy, with a low around 46. North northwest wind between 5 and 8 mph becoming calm. Sunday: Partly sunny, with a high near 68. Southwest wind 5 to 7 mph becoming west northwest. Sunday Night: Mostly clear, with a low around 47. Monday: Partly cloudy, with a high near 72. Monday Night: Increasing clouds, with a low around 48. Tuesday: Mostly cloudy with occasional light rain, with a high near 67. Tuesday Night: Mostly cloudy with occasional light rain, with a low around 48. Wednesday: Mostly cloudy early then partly sunny, with a high near 70. Wednesday Night: Partly cloudy, with a low around 50. Thursday: Partly sunny, with a high near 72. Notes: 1. Mixing height, as used here, is the lowest height at which the potential temperature exceeds the potential temperature at the surface. As a practical matter it is the approximate height to which a smoke plume will rise assuming good ignition, dry fuels, and winds less than about 15mph. 2. Transport winds are a layer average through the mixing height, weighted slightly toward the winds at the top of the layer. 3. Ventilation Index is the height of the mixing layer times the transport wind speed divided by 1000. 4. Surface wind direction is the general expected wind direction. At a specific point surface winds are highly dependent on local terrain conditions. This forecast is provided under an agreement between the Oregon Department of Agriculture and the Oregon Department of Forestry. For information contact ODA at 503-986-4701. -------------- next part -------------- An HTML attachment was scrubbed... URL: From willamette-fcst at listsmart.osl.state.or.us Tue Sep 7 08:45:49 2010 From: willamette-fcst at listsmart.osl.state.or.us (Willamette Valley Field Burning Forecast) Date: Tue, 7 Sep 2010 08:45:49 -0700 Subject: [willamette-fcst] Tue, 07 Sep 2010 Message-ID: SILVERTON HILLS FIELD BURNING FORECAST OREGON DEPARTMENT OF FORESTRY WEATHER OFFICE 9:00 AM PDT TUE SEP 07 2010 BURN ADVISORY: Recommended burn times for agricultural burning are from 9:00am to 5:30pm. Prep burning is allowed from 2:00pm to 5:00pm with a 50 acre limit. Propane flaming is allowed from 2:00pm to 5:00pm. WEATHER DISCUSSION: Upper air charts show a northwesterly flow over the Pacific Northwest this morning. Embedded in that flow is an upper disturbance located off the coast of central British Columbia. This will drop into the region tomorrow and carve out an upper level trough that will linger until about Thursday. Satellite pictures show a band of clouds centered on a line from south-central Washington to SW Oregon. To the northwest of that cloud band is an area of showers. Rainfall totals so far this morning have ammounted to just a couple of hundredths to a little less than a tenth of an inch so far. The morning sounding showed some cooling aloft and a fairly unstable atmosphere. Cloud cover will hold temperatures about 10 degrees below average for this time of year however, and the cool surface temperatures will limit mixing heights somewhat. Maximum Mixing heights will be around 3900 feet this afternoon. Pressure gradients, and consequently transport winds, will be quite light today. While the Newport to Salem gradient was 0.7mb onshore and the Salem to Redmond gradient was 0.4 onshore at 8:00am this morning, models indicate gradient stacking to the east will increase this afternoon. For the mid Willamette Valley expect mostly cloudy skies today with scattered light showers this afternoon. Salem's high temperature today will be near 69 and the minimum relative humidity will drop to about 53% Sunset tonight: 7:32 pm THREE-HOURLY DATA: 11am 2pm 5pm 8pm Temperature: 64 68 69 62 Relative Humidity: 70% 57% 53% 67% Surface Wind Direction: 170 200 240 290 Surface Wind Speed: 4 4 5 4 Transport Wind Direction: 300 250 280 290 Transport Wind Speed: 5 5 5 3 Estimated Mixing Height: 2800 3500 3900 500 Ventilation Index: 14 18 20 2 EXTENDED DISCUSSION: Models indicate onshore flow continuing but gradient stacking to the east for at least the next two days. The upper level trough will move to the east Friday and temporary ridging will set up over the region for more sunshine. Another trough moves in over the weekend for cooler temperatures. The details of the trough are not clear at this point but there is a potential for at least some rain at some point over the weekend. EXTENDED FORECAST: Wednesday: Mostly cloudy, a few showers. Wind SW 6 mph. Chance of precip 30%. Thursday: Partly sunny, with a high near 69. Calm wind becoming west southwest around 6 mph. Friday: Mostly sunny, with a high near 71. Saturday: Partly sunny, with a high near 71. Sunday: Mostly cloudy, with a high near 70. Monday: Partly sunny, with a high near 72. Notes: 1. Mixing height, as used here, is the lowest height at which the potential temperature exceeds the potential temperature at the surface. As a practical matter it is the approximate height to which a smoke plume will rise assuming good ignition, dry fuels, and winds less than about 15mph. 2. Transport winds are a layer average through the mixing height, weighted slightly toward the winds at the top of the layer. 3. Ventilation Index is the height of the mixing layer times the transport wind speed divided by 1000. 4. Surface wind direction is the general expected wind direction. At a specific point surface winds are highly dependent on local terrain conditions. This forecast is provided under an agreement between the Oregon Department of Agriculture and the Oregon Department of Forestry. For information contact ODA at 503-986-4701. -------------- next part -------------- An HTML attachment was scrubbed... URL: From willamette-fcst at listsmart.osl.state.or.us Tue Sep 7 11:44:20 2010 From: willamette-fcst at listsmart.osl.state.or.us (Willamette Valley Field Burning Forecast) Date: Tue, 7 Sep 2010 11:44:20 -0700 Subject: [willamette-fcst] Tue, 09 Sep 2010 Message-ID: SILVERTON HILLS FIELD BURNING FORECAST OREGON DEPARTMENT OF FORESTRY WEATHER OFFICE 12:00 PM PDT TUE SEP 07 2010 BURN ADVISORY: Recommended burn times for agricultural burning are up until 5:30pm tonight. Prep burning is allowed from 2:00pm to 5:00pm with a 50 acre limit. Propane flaming is allowed from 2:00pm to 5:00pm. WEATHER DISCUSSION: Satellite pictures show clouds covering much of the Willamette Valley as of late morning. As of 11:15am radar showed an area of significant precipitation over Benton County, moving ENE toward the Silvertion Hills grass growing region. Radar estimates indicate over an inch of rain has fallen in the coast range west of Corvallis during the morning hours. However, so far, the Corvallis airport has picked up just .05 in the last 24 hours. It is likely that rain will continue into the afternoon for much of the mid Willamette Valley. At 11:00am the Salem Airport was reporting a broken cloud layer at 800 feet, another at 1700 feet and the base of the overcast layer was at 3000 feet. This morning's sounding showed some cooling aloft and a fairly unstable atmosphere. Cloud cover will hold temperatures about 10-14 degrees below average for this time of year however, and the cool surface temperatures will limit mixing heights somewhat. Maximum mixing heights will be around 3200 feet this afternoon. Pressure gradients, and consequently transport winds, will be quite light today. While the Newport to Salem gradient was 0.9mb onshore and the Salem to Redmond gradient was 0.7mb onshore at 11:00am this morning, models indicate gradient stacking to the east will increase this afternoon. For the mid Willamette Valley expect mostly cloudy skies today with scattered light showers this afternoon. Salem's high temperature today will be near 64 and the minimum relative humidity will drop to about 59% Sunset tonight: 7:32 pm THREE-HOURLY DATA: 2pm 5pm 8pm Temperature: 63 63 62 Relative Humidity: 63% 61% 72% Surface Wind Direction: 200 310 320 Surface Wind Speed: 6 6 4 Transport Wind Direction: 250 280 290 Transport Wind Speed: 5 5 3 Estimated Mixing Height: 3200 3200 500 Ventilation Index: 16 16 2 EXTENDED DISCUSSION: Models indicate onshore flow continuing but gradient stacking to the east for at least the next two days. The upper level trough will move to the east Friday and temporary ridging will set up over the region for more sunshine. Another trough moves in over the weekend for cooler temperatures. The details of the trough are not clear at this point but there is a potential for at least some rain at some point over the weekend. EXTENDED FORECAST: Wednesday: Mostly cloudy, a few showers. Wind SW 6 mph. Chance of precip 30%. Thursday: Partly sunny, with a high near 69. Calm wind becoming west southwest around 6 mph. Friday: Mostly sunny, with a high near 71. Saturday: Partly sunny, with a high near 71. Sunday: Mostly cloudy, with a high near 70. Monday: Partly sunny, with a high near 72. Notes: 1. Mixing height, as used here, is the lowest height at which the potential temperature exceeds the potential temperature at the surface. As a practical matter it is the approximate height to which a smoke plume will rise assuming good ignition, dry fuels, and winds less than about 15mph. 2. Transport winds are a layer average through the mixing height, weighted slightly toward the winds at the top of the layer. 3. Ventilation Index is the height of the mixing layer times the transport wind speed divided by 1000. 4. Surface wind direction is the general expected wind direction. At a specific point surface winds are highly dependent on local terrain conditions. This forecast is provided under an agreement between the Oregon Department of Agriculture and the Oregon Department of Forestry. For information contact ODA at 503-986-4701. -------------- next part -------------- An HTML attachment was scrubbed... URL: From willamette-fcst at listsmart.osl.state.or.us Wed Sep 8 11:33:24 2010 From: willamette-fcst at listsmart.osl.state.or.us (Willamette Valley Field Burning Forecast) Date: Wed, 8 Sep 2010 11:33:24 -0700 Subject: [willamette-fcst] Wed, 08 Sep 2010 Message-ID: SILVERTON HILLS FIELD BURNING FORECAST OREGON DEPARTMENT OF FORESTRY WEATHER OFFICE 12:00 PM PDT WED SEP 08 2010 BURN ADVISORY: Recommended burn times for agricultural burning are from 1:00pm to 5:30pm. Prep burning is not allowed due to high humidity. Propane flaming is not allowed due to high humidity. WEATHER DISCUSSION: An upper level low pressure area is situated over south central Washington at late morning. This is making the atmosphere unstable and scattered showers cover much of the Pacific Northwest. As surface temperatures warm, instability in the atmosphere will be released and additional showers will develop. Some of these showers will be quite significant with locally heavy rain and possibly thunder and lightning. The ODF late morning surface analysis shows onshore low level flow with gradient stacking to the east. Gradient stacking will likely continue throughout the day. The morning Salem sounding showed temperatures had cooled slightly since yesterday at all levels from the surface to above 14,000 feet. The temperature/moisture profile was conditionally unstable - supporting a strong shower or thunderstorm forecast for this afternoon. For the mid Willamette Valley, expect showers, heavy at times, for this afternoon with the possibility of a thunderstorm. Winds will be light westerly except gusty near showers. Salem's high temperature today will be near 66. Minimum relative humidity will be about 60%. Sunset tonight: 7:30 pm THREE-HOURLY DATA: 2pm 5pm 8pm Temperature: 65 66 59 Relative Humidity: 60% 60% 72% Surface Wind Direction: 210 270 270 Surface Wind Speed: 5 5 5 Transport Wind Direction: 220 280 270 Transport Wind Speed: 4 9 6 Estimated Mixing Height: 5000 5000 500 Ventilation Index: 20 45 3 EXTENDED DISCUSSION: The upper level low will move east of the area during the day tomorrow for a decreasing chance of showers. Models indicate a continuing onshore flow for mostly cloudy skies and poor field drying conditions. In addition models indicate gradient stacking to the east continuing. For Friday a flat ridge builds for some sun but the gradient stacking will likely continue. Over the weekend another upper level low will move down the coast of British Columbia and help carve out a weak upper trough over the Pacific Northwest. At this point it looks like most moisture should stay just north of the mid Willamette Valley. Onshore flow will keep temperatures a bit below average and there will be a mixture of clouds and sun. EXTENDED FORECAST: Thursday: Mostly cloudy, with a high near 67. Wind W 6. Friday: Partly sunny, with a high near 69. Wind NW 6. Saturday: Partly sunny, with a high near 70. Sunday: Mostly cloudy, with a high near 70. Monday: Partly sunny, with a high near 73. Tuesday: Partly sunny, with a high near 74. Notes: 1. Mixing height, as used here, is the lowest height at which the potential temperature exceeds the potential temperature at the surface. As a practical matter it is the approximate height to which a smoke plume will rise assuming good ignition, dry fuels, and winds less than about 15mph. 2. Transport winds are a layer average through the mixing height, weighted slightly toward the winds at the top of the layer. 3. Ventilation Index is the height of the mixing layer times the transport wind speed divided by 1000. 4. Surface wind direction is the general expected wind direction. At a specific point surface winds are highly dependent on local terrain conditions. This forecast is provided under an agreement between the Oregon Department of Agriculture and the Oregon Department of Forestry. For information contact ODA at 503-986-4701. -------------- next part -------------- An HTML attachment was scrubbed... URL: From willamette-fcst at listsmart.osl.state.or.us Wed Sep 8 08:38:14 2010 From: willamette-fcst at listsmart.osl.state.or.us (Willamette Valley Field Burning Forecast) Date: Wed, 8 Sep 2010 08:38:14 -0700 Subject: [willamette-fcst] Wed, 08 Sep 2010 Message-ID: SILVERTON HILLS FIELD BURNING FORECAST OREGON DEPARTMENT OF FORESTRY WEATHER OFFICE 9:00 AM PDT WED SEP 08 2010 BURN ADVISORY: Recommended burn times for agricultural burning are from 1:00pm to 5:30pm. Prep burning is not allowed due to high humidity. Propane flaming is not allowed due to high humidity. WEATHER DISCUSSION: An upper level low pressure area is situated over the southern Washington Cascades this morning. This is making the atmosphere unstable and areas of showers cover much of the Pacific Northwest. One line of showers extends from the northern Washington Cascades, across the southern Puget Sound region and then to about Longview, Washington. If present trajectories continue this should rotate into the central Willamette Valley later this morning. As surface temperatures warm instability in the atmosphere will be released and even more showers will develop. Some of these showers will be quite significant with locally heavy rain and possibly thunder and lightning. The ODF morning surface analysis shows onshore low level flow with gradient stacking to the east. Gradient stacking will likely continue throughout the day. Wet fields will be an issue today as well. Twenty-four rainfall totals as of this morning included: Salem Airport, .18; Jordan Valley, .16; Silverton, .28; and Turner, .32 inches. The morning Salem sounding showed temperatures had cooled slightly since yesterday at all levels from the surface to above 14,000 feet. The temperature/moisture profile was conditionally unstable - supporting a strong shower or thunderstorm forecast for this afternoon. For the mid Willamette Valley, expect showers, heavy at times, for this afternoon with the possibility of a thunderstorm. Winds will be light westerly except gusty near showers. Salem's high temperature today will be near 66. Minimum relative humidity will be about 60%. Sunset tonight: 7:30 pm THREE-HOURLY DATA: 11am 2pm 5pm 8pm Temperature: 59 65 66 59 Relative Humidity: 78% 60% 60% 72% Surface Wind Direction: 260 210 270 270 Surface Wind Speed: 2 5 5 5 Transport Wind Direction: 230 220 280 270 Transport Wind Speed: 4 4 9 6 Estimated Mixing Height: 3500 5000 5000 500 Ventilation Index: 14 20 45 3 EXTENDED DISCUSSION: The upper level low will move east of the area during the day tomorrow for a decreasing chance of showers. Models indicate a continuing onshore flow for mostly cloudy skies and poor field drying conditions. In addition models indicate gradient stacking to the east continuing. For Friday a flat ridge builds for some sun but the gradient stacking will likely continue. Over the weekend another upper level low will move down the coast of British Columbia and help carve out a weak upper trough over the Pacific Northwest. At this point it looks like most moisture should stay just north of the mid Willamette Valley. Onshore flow will keep temperatures a bit below average and there will be a mixture of clouds and sun. EXTENDED FORECAST: Thursday: Mostly cloudy, with a high near 67. Wind W 6. Friday: Partly sunny, with a high near 69. Wind NW 6. Saturday: Partly sunny, with a high near 70. Sunday: Mostly cloudy, with a high near 70. Monday: Partly sunny, with a high near 73. Tuesday: Partly sunny, with a high near 74. Notes: 1. Mixing height, as used here, is the lowest height at which the potential temperature exceeds the potential temperature at the surface. As a practical matter it is the approximate height to which a smoke plume will rise assuming good ignition, dry fuels, and winds less than about 15mph. 2. Transport winds are a layer average through the mixing height, weighted slightly toward the winds at the top of the layer. 3. Ventilation Index is the height of the mixing layer times the transport wind speed divided by 1000. 4. Surface wind direction is the general expected wind direction. At a specific point surface winds are highly dependent on local terrain conditions. This forecast is provided under an agreement between the Oregon Department of Agriculture and the Oregon Department of Forestry. For information contact ODA at 503-986-4701. -------------- next part -------------- An HTML attachment was scrubbed... URL: From willamette-fcst at listsmart.osl.state.or.us Thu Sep 9 08:32:10 2010 From: willamette-fcst at listsmart.osl.state.or.us (Willamette Valley Field Burning Forecast) Date: Thu, 9 Sep 2010 08:32:10 -0700 Subject: [willamette-fcst] Thu, 09 Sep 10 Message-ID: SILVERTON HILLS FIELD BURNING FORECAST OREGON DEPARTMENT OF FORESTRY WEATHER OFFICE 9:00 AM PDT THU SEP 09 2010 BURN ADVISORY: Recommended burn times for agricultural burning are from 10:00am to 5:30pm. Prep burning is allowed from 1:00pm to 5:00pm with a 50 acre limit. Propane flaming is allowed from 1:00pm to 5:00pm. WEATHER DISCUSSION: Upper air charts show an upper level low over north-central Washington this morning with a trough extending southwest with its axis just east of the Cascade crest. This will all move gradually eastward this afternoon for a slowly stabilizing airmass. Radar indicates most showers are over and east of the mountains this morning, but there still could be a few scattered showers in the foothills through this morning. The morning Salem sounding looked very similar to yesterday's. The main difference is that it was slightly drier between 1500 and 4000 feet. It is still conditionally unstable and in spite of the upper trough moving east models are showing very little warming aloft for significant stabilization. Consequently mixing heights will be quite high today, peaking near 6000 feet. Transport wind directions this morning are about 290 at 10. Computer models suggest a generally westerly flow continuing in the transport region during the day today. Impediments to open field burning are mainly the wet fields. The Salem airport picked up .12 inches of rain yesterday. Cloud cover and high humidities will not be conducive to much drying today. Gradient stacking to the east will also be an issue. Pressure gradients as of 8am included: Newport to Salem, 0.8 mb onshore and Salem to Redmond, 1.9 onshore. The RUC computer model shows the east-west pressure profile becoming favorable this afternoon while the NAM does not. We will monitor this through the day. For the mid Willamett Valley today expect mostly cloudy skies. There may be a few showers, especially toward the Cascade foothills this morning. Winds will be from the south-southwest during the morning becoming more west-southwesterly during the afternoon. Salem's high temperature today will be near 68. Minimum relative humidity will be near 51%. Sunset tonight: 7:28 pm THREE-HOURLY DATA: 11am 2pm 5pm 8pm Temperature: 63 67 67 60 Relative Humidity: 65% 54% 52% 67% Surface Wind Direction: 200 220 230 260 Surface Wind Speed: 5 5 5 5 Transport Wind Direction: 230 240 260 250 Transport Wind Speed: 10 13 14 6 Estimated Mixing Height: 3500 5800 6000 500 Ventilation Index: 35 75 84 3 EXTENDED DISCUSSION: A weak ridge develops late this afternoon and evening over the region. There will be minor disturbances moving through the ridge, but at this point it does not look like there will be any rain this far south. Temperatures will remain cooler than average into the weekend. The NAM model indicates gradient stacking to the east both tomorrow and Saturday. Longer range charts have turned more optimistic with ridging building the first part of next week for drier weather and temperatures returning to near average for mid September. EXTENDED FORECAST: Tomorrow: Partly sunny, 72. Wind becoming NNW 5-8 mph. Saturday: Partly sunny, 74. Wind becoming NW 6 mph. Sunday: Mostly cloudy, with a high near 74. Monday: Partly sunny, with a high near 80. Tuesday: Partly sunny, with a high near 79. Wednesday: Partly sunny, with a high near 77. Notes: 1. Mixing height, as used here, is the lowest height at which the potential temperature exceeds the potential temperature at the surface. As a practical matter it is the approximate height to which a smoke plume will rise assuming good ignition, dry fuels, and winds less than about 15mph. 2. Transport winds are a layer average through the mixing height, weighted slightly toward the winds at the top of the layer. 3. Ventilation Index is the height of the mixing layer times the transport wind speed divided by 1000. 4. Surface wind direction is the general expected wind direction. At a specific point surface winds are highly dependent on local terrain conditions. This forecast is provided under an agreement between the Oregon Department of Agriculture and the Oregon Department of Forestry. For information contact ODA at 503-986-4701. -------------- next part -------------- An HTML attachment was scrubbed... URL: From willamette-fcst at listsmart.osl.state.or.us Thu Sep 9 11:38:49 2010 From: willamette-fcst at listsmart.osl.state.or.us (Willamette Valley Field Burning Forecast) Date: Thu, 9 Sep 2010 11:38:49 -0700 Subject: [willamette-fcst] Thu, 09 Sep 10 Message-ID: SILVERTON HILLS FIELD BURNING FORECAST OREGON DEPARTMENT OF FORESTRY WEATHER OFFICE 12:00 PM PDT THU SEP 09 2010 BURN ADVISORY: Recommended burn times for agricultural burning are from 10:00am to 5:30pm. Prep burning is allowed from 1:00pm to 5:00pm with a 50 acre limit. Propane flaming is allowed from 1:00pm to 5:00pm. WEATHER DISCUSSION: Upper air charts show an upper level trough beginning to pull out of the Pacific Northwest and a weak upper level ridge developing to the northwest. The morning Salem sounding was very similar to yesterday's. The main difference was that it indicated slightly drier air between 1500 and 4000 feet. It is still conditionally unstable and in spite of the upper trough moving east models are showing very little warming aloft for significant stabilization. Consequently mixing heights will be quite high today, peaking near 6000 feet. Transport wind directions on the morning sounding were about 290 at 10. Computer models suggest a generally westerly flow continuing in the transport region during the day today. With rain the past few days and mostly cloudy skies this morning and high humidities, dry fields will be an issue for open field burning this afternoon. If any growers feel their fields are dry enough to burn today they need to make that known to field burning staff. Gradient stacking to the east will also be an issue this afternoon. Pressure gradients as of 11am included: Newport to Salem, 1.2 mb onshore; Salem to Redmond, 2.6 mb onshore. The the latest RUC computer model shows the east-west pressure profile becoming marginally favorable this afternoon while the NAM is marginally unfavorable. We will monitor this through the day. For the mid Willamett Valley today expect mostly cloudy skies. There may be a few showers, especially toward the Cascade foothills this morning. Winds will be from the south-southwest during the morning becoming more west-southwesterly during the afternoon. Salem's high temperature today will be near 68. Minimum relative humidity will be near 51%. Sunset tonight: 7:28 pm THREE-HOURLY DATA: 2pm 5pm 8pm Temperature: 67 67 60 Relative Humidity: 54% 52% 67% Surface Wind Direction: 220 230 260 Surface Wind Speed: 5 5 5 Transport Wind Direction: 240 260 250 Transport Wind Speed: 13 14 6 Estimated Mixing Height: 5800 6000 500 Ventilation Index: 75 84 3 EXTENDED DISCUSSION: Latest computer models still show a ridge developing late this afternoon and evening over the region. There will be minor disturbances moving through the ridge, but at this point it still does not look like there will be any rain this far south. Temperatures will remain cooler than average into the weekend. The latest NAM model continues to show gradient stacking to the east both tomorrow and Saturday. Longer range charts have turned more optimistic with ridging building the first part of next week for drier weather and temperatures returning to near average for mid September. EXTENDED FORECAST: Tomorrow: Partly sunny, 72. Wind becoming NNW 5-8 mph. Saturday: Partly sunny, 74. Wind becoming NW 6 mph. Sunday: Mostly cloudy, with a high near 74. Monday: Partly sunny, with a high near 80. Tuesday: Partly sunny, with a high near 79. Wednesday: Partly sunny, with a high near 77. Notes: 1. Mixing height, as used here, is the lowest height at which the potential temperature exceeds the potential temperature at the surface. As a practical matter it is the approximate height to which a smoke plume will rise assuming good ignition, dry fuels, and winds less than about 15mph. 2. Transport winds are a layer average through the mixing height, weighted slightly toward the winds at the top of the layer. 3. Ventilation Index is the height of the mixing layer times the transport wind speed divided by 1000. 4. Surface wind direction is the general expected wind direction. At a specific point surface winds are highly dependent on local terrain conditions. This forecast is provided under an agreement between the Oregon Department of Agriculture and the Oregon Department of Forestry. For information contact ODA at 503-986-4701. -------------- next part -------------- An HTML attachment was scrubbed... URL: From willamette-fcst at listsmart.osl.state.or.us Fri Sep 10 08:31:59 2010 From: willamette-fcst at listsmart.osl.state.or.us (Willamette Valley Field Burning Forecast) Date: Fri, 10 Sep 2010 08:31:59 -0700 Subject: [willamette-fcst] September 10 Message-ID: SILVERTON HILLS FIELD BURNING FORECAST OREGON DEPARTMENT OF FORESTRY WEATHER OFFICE 9:00 AM PDT FRI SEP 10 2010 BURN ADVISORY: Recommended burn times for agricultural burning are from 1:00pm to 5:30pm. Prep burning is not allowed due to staff unavailability. Propane flaming is not allowed due to staff unavailability. WEATHER DISCUSSION: Weak upper level ridge will build into the state this morning but quickly slide to the east later today and tonight as a minor trough moves in. Weather pattern is fairly innocuous with little pressure gradient and little wind. Morning sounding shows a fairly strong surface-based temperature inversion up to a few hundred feet then a modestly stable temperature sounding above. Afternoon heating will gradually lift mixing levels up into the 4000 - 5000 ft range. Expect a mostly fair day with morning low clouds and fog slowly giving way to afternoon sunshine as clouds clear from the south to north. Pressure gradients are weak this morning with the Newport to Salem gradient .4 mb onshore and the Salem to Redmond gradient .9 mb offshore. With surface heating today that pressure gradient will become increasingly onshore with fairly even stacking between the Coast Range and Cascades. Salem's high temperature today will be near 72. Relative humidity drops to 50% by 1pm. Minimum relative humidity 39%. Wind flow will be light and variable during the morning becoming northwesterly in the afternoon. Some models show a nearly northerly flow. Will have to monitor with pibals this afternoon to determine if there will be any usuability to the wind for burning. Sunset tonight: 7:27 pm THREE-HOURLY DATA: 11am 2pm 5pm 8pm Temperature: 62 69 72 65 Relative Humidity: 65% 45% 39% 54% Surface Wind Direction: 190 300 340 310 Surface Wind Speed: 3 5 6 5 Transport Wind Direction: 230 330 320 340 Transport Wind Speed: 5 7 7 7 Estimated Mixing Height: 2200 4200 4800 1000 Ventilation Index: 11 29 34 7 EXTENDED DISCUSSION: Weak troughing moves in over the state early tomorrow as an upper level low moves by to the north. Trough then moves by to the east during the afternoon. This will have little effect on the weather with another pleasant warm day and mostly sunny skies after some morning low clouds. Pressure gradients will be mostly weak with a slight onshore flow in the afternoon. Another minor trough moves by to the north on Sunday with a ridge moving in later Monday and Tuesday. Temperatures will gradually warm up through the extended period. Upper ridge generally holds through the period as well. Pressure gradients and wind flow will be rather weak with light northerly to offshore flow in the morning and northerly to onshore flow in the afternoon. EXTENDED FORECAST: Saturday: Partly sunny, with a high near 74. North northwest wind between 3 and 8 mph. Saturday Night: Partly cloudy, with a low around 48. North northwest wind between 4 and 7 mph becoming calm. Sunday: Partly sunny, with a high near 77. Calm wind becoming north northwest between 4 and 7 mph. Sunday Night: Partly cloudy, with a low around 51. Monday: Sunny, with a high near 77. Monday Night: Mostly clear, with a low around 49. Tuesday: Sunny, with a high near 80. Tuesday Night: Mostly clear, with a low around 50. Wednesday: Mostly sunny, with a high near 79. Wednesday Night: Partly cloudy, with a low around 52. Thursday: Mostly sunny, with a high near 80. Notes: 1. Mixing height, as used here, is the lowest height at which the potential temperature exceeds the potential temperature at the surface. As a practical matter it is the approximate height to which a smoke plume will rise assuming good ignition, dry fuels, and winds less than about 15mph. 2. Transport winds are a layer average through the mixing height, weighted slightly toward the winds at the top of the layer. 3. Ventilation Index is the height of the mixing layer times the transport wind speed divided by 1000. 4. Surface wind direction is the general expected wind direction. At a specific point surface winds are highly dependent on local terrain conditions. This forecast is provided under an agreement between the Oregon Department of Agriculture and the Oregon Department of Forestry. For information contact ODA at 503-986-4701. -------------- next part -------------- An HTML attachment was scrubbed... URL: From willamette-fcst at listsmart.osl.state.or.us Fri Sep 10 11:45:29 2010 From: willamette-fcst at listsmart.osl.state.or.us (Willamette Valley Field Burning Forecast) Date: Fri, 10 Sep 2010 11:45:29 -0700 Subject: [willamette-fcst] September 10 Message-ID: SILVERTON HILLS FIELD BURNING FORECAST OREGON DEPARTMENT OF FORESTRY WEATHER OFFICE 12:00 PM PDT FRI SEP 10 2010 BURN ADVISORY: Recommended burn times for agricultural burning are from 1:00pm to 5:30pm. Prep burning is not allowed. Propane flaming is not allowed. WEATHER DISCUSSION: Weak upper level ridge will build into the state today but will quickly slide to the east later tonight as a minor trough moves in. Weather pattern is fairly innocuous with little pressure gradient and little wind. Morning sounding showed a fairly strong surface-based temperature inversion up to a few hundred feet then a modestly stable temperature sounding above. Based on the sounding the current mixing height is near 2500 ft. Afternoon heating will gradually lift mixing levels up to 4000 - 5000 ft. Expect a mostly fair day with morning clouds slowly giving way to afternoon sunshine as clouds clear from the south to north. Pressure gradients are weak this morning with the Newport to Salem gradient .6 mb onshore and the Salem to Redmond gradient .8 mb onshore. With surface heating today that pressure gradient will become increasingly onshore with fairly even stacking between the Coast Range and Cascades. Salem's high temperature today will be near 72. Relative humidity drops to 50% by 1 pm. Minimum relative humidity near 40%. Wind flow is currently light SW'erly but should turn northwesterly during the afternoon. Some models show a nearly northerly flow. Will have to monitor with pibals this afternoon to determine if there will be any usuability to the wind for burning. Sunset tonight: 7:27 pm THREE-HOURLY DATA: 2pm 5pm 8pm Temperature: 69 72 65 Relative Humidity: 45% 39% 54% Surface Wind Direction: 300 340 310 Surface Wind Speed: 5 6 5 Transport Wind Direction: 320 320 340 Transport Wind Speed: 7 7 7 Estimated Mixing Height: 4200 4800 1000 Ventilation Index: 29 34 7 EXTENDED DISCUSSION: Weak troughing moves in over the state early tomorrow as an upper level low moves by to the north. Trough then moves by to the east during the afternoon. This will have little effect on the weather with another pleasant warm day and mostly sunny skies after some morning low clouds. Pressure gradients will be mostly weak with a slight onshore flow in the afternoon. Another minor trough moves by to the north on Sunday with a ridge moving in later Monday and Tuesday. Temperatures will gradually warm up through the extended period. Upper ridge generally holds through the period as well. Pressure gradients and wind flow will be rather weak with light northerly to offshore flow in the morning and northerly to onshore flow in the afternoon. EXTENDED FORECAST: Saturday: Partly sunny, with a high near 74. North northwest wind between 3 and 8 mph. Saturday Night: Partly cloudy, with a low around 48. North northwest wind between 4 and 7 mph becoming calm. Sunday: Partly sunny, with a high near 78. Calm wind becoming north northwest between 4 and 7 mph. Sunday Night: Partly cloudy, with a low around 51. Monday: Sunny, with a high near 79. Monday Night: Mostly clear, with a low around 49. Tuesday: Sunny, with a high near 80. Tuesday Night: Mostly clear, with a low around 50. Wednesday: Mostly sunny, with a high near 79. Wednesday Night: Partly cloudy, with a low around 52. Thursday: Mostly sunny, with a high near 80. Notes: 1. Mixing height, as used here, is the lowest height at which the potential temperature exceeds the potential temperature at the surface. As a practical matter it is the approximate height to which a smoke plume will rise assuming good ignition, dry fuels, and winds less than about 15mph. 2. Transport winds are a layer average through the mixing height, weighted slightly toward the winds at the top of the layer. 3. Ventilation Index is the height of the mixing layer times the transport wind speed divided by 1000. 4. Surface wind direction is the general expected wind direction. At a specific point surface winds are highly dependent on local terrain conditions. This forecast is provided under an agreement between the Oregon Department of Agriculture and the Oregon Department of Forestry. For information contact ODA at 503-986-4701. -------------- next part -------------- An HTML attachment was scrubbed... URL: From willamette-fcst at listsmart.osl.state.or.us Mon Sep 13 08:39:46 2010 From: willamette-fcst at listsmart.osl.state.or.us (Willamette Valley Field Burning Forecast) Date: Mon, 13 Sep 2010 08:39:46 -0700 Subject: [willamette-fcst] Mon, 13 Sep 10 Message-ID: SILVERTON HILLS FIELD BURNING FORECAST OREGON DEPARTMENT OF FORESTRY WEATHER OFFICE 9:00 AM PDT MON SEP 13 2010 BURN ADVISORY: Agricultural burning burning is not recommended. Prep burning is allowed from 12:30pm to 5:00pm with a 50 acre limit. Propane flaming is not allowed. WEATHER DISCUSSION: Upper air charts show a weak ridge aloft with a minor embedded disturbance off the southwest Oregon coast. Satellite pictures show low covering clouds parts of the Willamette Valley this morning as well as some scattered high clouds associated with the upper disturbance. Areas with cloud cover are running about 10 degrees warmer this morning versus yesterday, other areas are about the same. The ODF morning surface analysis shows high pressure nosing into western Washington and a well developed thermal trough in extending into northern California. This is giving a northerly gradient to the Willamette Valley that will likely produce north or north-northeast transport winds throughout the day. This is not favorable for open field burning. The morning Salem sounding showed a slightly warmer airmass this morning from about 2300 feet to about 8500 feet. There is a small inversion between 1800 and 2500 feet. This inversion will easily mix out with some afternoon sunshine and mixng heights today will climb to 3500 feet. The morning Salem sounding also showed those north-northeast transport winds. Wind direction will likely be the major factor in preventing open field burning this afternoon. The low clouds in the valley should burn off by late morning. The upper disturbance off the SW Coast will rotate inland and could touch off a few showers or thunderstorms over the southern and central Oregon Cascades this afternoon. For the mid Willamette Valley expect clouds this morning, turning sunny this afternoon with light northerly winds. Salem's high temperature today will be near 81. Relative humidity drops to 50% by noon. Minimum relative humidity 37%. Sunset tonight: 7:21 pm THREE-HOURLY DATA: 11am 2pm 5pm 8pm Temperature: 69 78 81 72 Relative Humidity: 61% 43% 37% 51% Surface Wind Direction: 010 010 010 310 Surface Wind Speed: 6 5 6 5 Transport Wind Direction: 360 360 360 360 Transport Wind Speed: 08 12 13 05 Estimated Mixing Height: 2200 3100 3500 500 Ventilation Index: 18 37 46 2 EXTENDED DISCUSSION: An upper level low will develop off the coast of British Columbia later today and tomorrow and drift southward to off the Oregon Coast. By later Wednesday this will edge closer to the coastline and could produce some light rain by Wednesday night. As this moves over the region the chances of rain will increase and remain elevated through the weekend. Models indicate a more westerly transport flow tomorrow. However, they also indicate gradient stacking to the east and pressure patterns may not turn favorable until early evening tomorrow. Even though conditions look only marginal, tomorrow looks to be the day with the best chance for open field burning this week, with Wednesday also a slight possibility. EXTENDED FORECAST: Tuesday: Mostly sunny, with a high near 80. NW 3-6. Wednesday: Mostly cloudy, 78. Chance of rain Wednesday evening. SW 6. Thursday: Chance of rain early then partly sunny, 75. Friday: A chance of rain. Partly sunny, with a high near 73. Saturday: A chance of rain. Mostly cloudy, with a high near 70. Sunday: A chance of rain. Mostly cloudy, with a high near 71. Notes: 1. Mixing height, as used here, is the lowest height at which the potential temperature exceeds the potential temperature at the surface. As a practical matter it is the approximate height to which a smoke plume will rise assuming good ignition, dry fuels, and winds less than about 15mph. 2. Transport winds are a layer average through the mixing height, weighted slightly toward the winds at the top of the layer. 3. Ventilation Index is the height of the mixing layer times the transport wind speed divided by 1000. 4. Surface wind direction is the general expected wind direction. At a specific point surface winds are highly dependent on local terrain conditions. This forecast is provided under an agreement between the Oregon Department of Agriculture and the Oregon Department of Forestry. For information contact ODA at 503-986-4701. -------------- next part -------------- An HTML attachment was scrubbed... URL: From willamette-fcst at listsmart.osl.state.or.us Mon Sep 13 11:49:00 2010 From: willamette-fcst at listsmart.osl.state.or.us (Willamette Valley Field Burning Forecast) Date: Mon, 13 Sep 2010 11:49:00 -0700 Subject: [willamette-fcst] Mon, 13 Sep 10 Message-ID: SILVERTON HILLS FIELD BURNING FORECAST OREGON DEPARTMENT OF FORESTRY WEATHER OFFICE 12:00 PM PDT MON SEP 13 2010 BURN ADVISORY: Agricultural burning burning is not recommended. Prep burning is allowed from 12:30pm to 5:00pm with a 50 acre limit. Propane flaming is not allowed. WEATHER DISCUSSION: Upper air charts show a weak ridge aloft with a minor embedded disturbance off the southwest Oregon coast. The low clouds in the Willamette Valley have been quite persistent through the morning hours. Satellite pictures show a narrow band of low clouds stretching from portland to about Roseburg. The base of the cloud deck is at about 1300 feet and pilot reports indicate tops are at about 2100 feet. We still should see the clouds burn off this afternoon. As of 11:00am this morning areas under the clouds were running 2-5 degrees cooler than yesterday. Cloud free areas were 2-5 degrees warmer. The clouds are thin enough that we still expect sunshine to break through this afternoon. The ODF late morning surface analysis shows higher pressure to the north and a thermal trough in the central Valley of California, extending northward into northern California. This is giving a northerly gradient to the Willamette Valley that will likely produce north or north-northeast transport winds throughout the day. This is not favorable for open field burning. The morning Salem sounding showed a slightly warmer airmass this morning from about 2300 feet to about 8500 feet. There is a small inversion between 1800 and 2500 feet. This inversion will easily mix out with some afternoon sunshine and mixng heights today will climb to 3500 feet. The morning Salem sounding also showed those north-northeast transport winds. Wind direction will likely be the major factor in preventing open field burning this afternoon. The upper disturbance off the SW Coast will rotate inland and could touch off a few showers or thunderstorms over the southern and central Oregon Cascades this afternoon. For the mid Willamette Valley expect skies to turn sunny this afternoon with light northerly winds. Salem's high temperature today will be near 78. Minimum relative humidity 42%. Sunset tonight: 7:21 pm THREE-HOURLY DATA: 11am 2pm 5pm 8pm Temperature: 69 74 78 72 Relative Humidity: 61% 48% 42% 51% Surface Wind Direction: 010 010 010 310 Surface Wind Speed: 6 5 6 5 Transport Wind Direction: 360 360 360 360 Transport Wind Speed: 08 12 13 05 Estimated Mixing Height: 2200 3100 3500 500 Ventilation Index: 18 37 46 2 EXTENDED DISCUSSION: An upper level low will develop off the coast of British Columbia later today and tomorrow and drift southward to off the Oregon Coast. By later Wednesday this will edge closer to the coastline and could produce some light rain by Wednesday night. As this moves over the region the chances of rain will increase and remain elevated through the weekend. Models indicate a more westerly transport flow tomorrow. However, they also indicate gradient stacking to the east and pressure patterns may not turn favorable until early evening tomorrow. Even though conditions look only marginal, tomorrow looks to be the day with the best chance for open field burning this week, with Wednesday also a slight possibility. EXTENDED FORECAST: Tuesday: Mostly sunny, with a high near 80. NW 3-6. Wednesday: Mostly cloudy, 78. Chance of rain Wednesday evening. SW 6. Thursday: Chance of rain early then partly sunny, 75. Friday: A chance of rain. Partly sunny, with a high near 73. Saturday: A chance of rain. Mostly cloudy, with a high near 70. Sunday: A chance of rain. Mostly cloudy, with a high near 71. Notes: 1. Mixing height, as used here, is the lowest height at which the potential temperature exceeds the potential temperature at the surface. As a practical matter it is the approximate height to which a smoke plume will rise assuming good ignition, dry fuels, and winds less than about 15mph. 2. Transport winds are a layer average through the mixing height, weighted slightly toward the winds at the top of the layer. 3. Ventilation Index is the height of the mixing layer times the transport wind speed divided by 1000. 4. Surface wind direction is the general expected wind direction. At a specific point surface winds are highly dependent on local terrain conditions. This forecast is provided under an agreement between the Oregon Department of Agriculture and the Oregon Department of Forestry. For information contact ODA at 503-986-4701. -------------- next part -------------- An HTML attachment was scrubbed... URL: From willamette-fcst at listsmart.osl.state.or.us Tue Sep 14 08:30:51 2010 From: willamette-fcst at listsmart.osl.state.or.us (Willamette Valley Field Burning Forecast) Date: Tue, 14 Sep 2010 08:30:51 -0700 Subject: [willamette-fcst] Tue, 14 Sep 10 Message-ID: SILVERTON HILLS FIELD BURNING FORECAST OREGON DEPARTMENT OF FORESTRY WEATHER OFFICE 9:00 AM PDT TUE SEP 14 2010 BURN ADVISORY: Agricultural burning burning is not recommended. Prep burning is allowed from 1:00pm to 5:00pm with a 50 acre limit. Propane flaming is not allowed. WEATHER DISCUSSION: A weak upper level ridge covers western Oregon this morning. To the east a small but active upper level disturbance is pulling out and to the west a strong but slow moving upper level low is developing. Satellite pictures show low clouds over portions of the Willamette Valley, but the cloud deck is not as extensive as yesterday. By afternoon the entire valley should be sunny with temperatures climbing into the low 80's which is about 5 to 7 degrees above the seasonal average for this time of year. The morning Salem sounding temperature profile looked similar to yesterday's. There was a weak inversion between 2200 feet and 2900 feet. Below the inversion winds were light north-easterly, above light north-westerly. The inversion should easily mix out and the maximum mixing height today should go above 4000 feet. The morning ODF surface analysis shows higher pressure to the north, lower pressure to the south for northerly winds today. Unfortunately this is not a favorable direction for burning. Computer models indicate a transition to southerly winds early this evening, but no indication of any sustained transport flow with a westerly component for a burn opportunity. Pibals this afternoon will confirm or deny the modeled winds. For the mid Willamette Valley look for mostly sunny skies today with light north to northwest winds. Salem's high temperature today will be near 81. Relative humidity drops to 50% by 12pm. Minimum relative humidity 35%. Sunset tonight: 7:19 pm THREE-HOURLY DATA: 11am 2pm 5pm 8pm Temperature: 69 78 81 73 Relative Humidity: 61% 42% 35% 48% Surface Wind Direction: 360 340 360 280 Surface Wind Speed: 2 3 4 4 Transport Wind Direction: 350 350 340 340 Transport Wind Speed: 3 5 5 3 Estimated Mixing Height: 2500 3300 4500 500 Ventilation Index: 8 16 22 2 EXTENDED DISCUSSION: Today may be the last of summer weather for 2010. The upper low to the west will continue to spin off the coast sending surges of moisture inland until the low itself finally weakens and moves across the region next Monday. EXTENDED FORECAST: Wednesday: Mostly cloudy,rain developing by evening. 74. Wind SW 3-8 Thursday: Mostly cloudy, periods of light rain. 76. Wind SW 3-8 Friday: A 50 percent chance of rain. Mostly cloudy, with a high near 73. Saturday: A chance of rain. Mostly cloudy, with a high near 70. Sunday: A chance of rain. Mostly cloudy, with a high near 71. Monday: A chance of rain. Mostly cloudy, with a high near 71. Notes: 1. Mixing height, as used here, is the lowest height at which the potential temperature exceeds the potential temperature at the surface. As a practical matter it is the approximate height to which a smoke plume will rise assuming good ignition, dry fuels, and winds less than about 15mph. 2. Transport winds are a layer average through the mixing height, weighted slightly toward the winds at the top of the layer. 3. Ventilation Index is the height of the mixing layer times the transport wind speed divided by 1000. 4. Surface wind direction is the general expected wind direction. At a specific point surface winds are highly dependent on local terrain conditions. This forecast is provided under an agreement between the Oregon Department of Agriculture and the Oregon Department of Forestry. For information contact ODA at 503-986-4701. -------------- next part -------------- An HTML attachment was scrubbed... URL: From willamette-fcst at listsmart.osl.state.or.us Tue Sep 14 11:31:13 2010 From: willamette-fcst at listsmart.osl.state.or.us (Willamette Valley Field Burning Forecast) Date: Tue, 14 Sep 2010 11:31:13 -0700 Subject: [willamette-fcst] TUE, 14 Sep 10 Message-ID: SILVERTON HILLS FIELD BURNING FORECAST OREGON DEPARTMENT OF FORESTRY WEATHER OFFICE 12:00 PDT TUE SEP 14 2010 BURN ADVISORY: Agricultural burning is not recommended. Prep burning is allowed from noon to 5:30pm. Propane flaming is allowed from noon to 4:30pm. WEATHER DISCUSSION: Satellite pictures still show some low clouds over portions of the Willamette Valley. There is a small patch of clouds over western Linn County, otherwise the clouds are mainly over extreme northern Marion County, western Clackamas County and most of Polk and Yamhill Counties. There is a weak upper level ridge over western Oregon today. About 600 miles west of Oregon a strong upper level low continues to develop. The late morning ODF surface analysis shows higher pressure to the north, lower pressure to the south for northerly winds today. Pressure gradients as of 11am included: Newport to Salem, 0.9 mb onshore; Salem to Redmond, 0.5 mb onshore; Newport to Redmond, 1.4 mb onshore; Portland to Eugene, 0.3 mb northerly; and Portland to Medford, 1.5 mb northerly. The morning Salem sounding temperature profile looked similar to yesterday's. There was a weak inversion between 2200 feet and 2900 feet. This inversion will mix out with a surface temperature of 74F and the maximum mixing height today should climb to above 4000 feet. For the mid Willamette Valley look for mostly sunny skies this afternoon with light northeast to northwest winds. Salem's high temperature today will be near 81. Relative humidity drops to 50% by 12pm. Minimum relative humidity 35%. Sunset tonight: 7:19 pm THREE-HOURLY DATA: 2pm 5pm 8pm Temperature: 78 81 73 Relative Humidity: 42% 35% 48% Surface Wind Direction: 340 360 280 Surface Wind Speed: 3 4 4 Transport Wind Direction: 350 340 340 Transport Wind Speed: 5 5 3 Estimated Mixing Height: 3300 4500 500 Ventilation Index: 16 22 2 EXTENDED DISCUSSION: Today may be the last of summer weather for 2010. The upper low to the west will continue to spin off the coast sending surges of moisture inland until the low itself finally weakens and moves across the region next Monday. EXTENDED FORECAST: Wednesday: Mostly cloudy,rain developing by evening. 74. Wind SW 3-8 Thursday: Mostly cloudy, periods of light rain. 76. Wind SW 3-8 Friday: A 50 percent chance of rain. Mostly cloudy, with a high near 73. Saturday: A chance of rain. Mostly cloudy, with a high near 70. Sunday: A chance of rain. Mostly cloudy, with a high near 71. Monday: A chance of rain. Mostly cloudy, with a high near 71. Notes: 1. Mixing height, as used here, is the lowest height at which the potential temperature exceeds the potential temperature at the surface. As a practical matter it is the approximate height to which a smoke plume will rise assuming good ignition, dry fuels, and winds less than about 15mph. 2. Transport winds are a layer average through the mixing height, weighted slightly toward the winds at the top of the layer. 3. Ventilation Index is the height of the mixing layer times the transport wind speed divided by 1000. 4. Surface wind direction is the general expected wind direction. At a specific point surface winds are highly dependent on local terrain conditions. This forecast is provided under an agreement between the Oregon Department of Agriculture and the Oregon Department of Forestry. For information contact ODA at 503-986-4701. -------------- next part -------------- An HTML attachment was scrubbed... URL: From willamette-fcst at listsmart.osl.state.or.us Wed Sep 15 08:56:46 2010 From: willamette-fcst at listsmart.osl.state.or.us (Willamette Valley Field Burning Forecast) Date: Wed, 15 Sep 2010 08:56:46 -0700 Subject: [willamette-fcst] Silverton Hills Forecast - WED, SEPTEMBER 15, 2010 Message-ID: SILVERTON HILLS FIELD BURNING FORECAST OREGON DEPARTMENT OF FORESTRY WEATHER OFFICE 9:00 AM PDT WED SEP 15, 2010 BURN ADVISORY: Agricultural burning burning is not recommended. Prep burning is allowed from 12:00pm to 2:00pm with a 50 acre limit. Propane flaming is allowed from 12:00pm to 2:00pm. WEATHER DISCUSSION: A weak cold front about 200 miles offshore has already spread clouds across most of Washington and the western half of Oregon. Radar is picking up some light rain offshore, but there were no reports of rain inland as of mid-morning. The surface map shows weak pressure gradients across western Oregon this morning with light winds in the Willamette Valley. Clouds should lower and thicken today with increasing south-southwesterly winds. The morning sounding showed fairly warm air aloft, and mixing heights will be slow to rise today due to the cloud-cover. There could be a brief window of opportunity for open burning this afternoon, if the approaching light rain holds off until this evening. Transport winds may be too southerly early in the afternoon and become too strong for good plume development later in the afternoon. TODAY'S FORECAST: Mostly cloudy. A chance of rain in the afternoon with rain likely this evening. After reaching 80 degrees on Tuesday, cloudy skies will hold the high temperature to near 75 degrees this afternoon. The mixing height will climb to near 3000 feet about noon and likely top out between 3000 and 4000 feet in the mid-afternoon, then drop below 3000 feet by 5 p.m. Relative humidity will drop to near 50% this afternoon with the ventilation index climbing to around 42. Silverton area sunset tonight: 7:17pm THREE-HOURLY DATA: 11am 2pm 5pm 8pm Temperature: 68 74 74 65 Relative Humidity: 65% 51% 51% 73% Surface Wind Direction: 170 190 210 190 Surface Wind Speed: 6 6 8 5 Transport Wind Direction: 190 200 230 200 Transport Wind Speed: 10 12 15 10 Estimated Mixing Height: 2000 3500 2500 1000 Ventilation Index: 20 42 38 10 EXTENDED DISCUSSION: A transitory ridge will bring a break from the rain on Thursday with another weather system slated to come onshore by Friday afternoon. Wet weather is forecast this weekend and perhaps into early next week. However, there does appear to be an opportunity for some drying of fields around the middle of next week. EXTENDED FORECAST: Thursday: Mostly cloudy. Chance of rain. High near 75. Friday: Rain likely by the afternoon. High near 72. Saturday: Rain likely. High near 70. Sunday: Mostly cloudy. Chance of rain. High near 70. Monday: A chance of showers. High near 73. Tuesday: Partly sunny. Slight chance of showers. High near 76. Notes: 1. Mixing height, as used here, is the lowest height at which the potential temperature exceeds the potential temperature at the surface. As a practical matter it is the approximate height to which a smoke plume will rise assuming good ignition, dry fuels, and winds less than about 15mph. 2. Transport winds are a layer average through the mixing height, weighted slightly toward the winds at the top of the layer. 3. Ventilation Index is the height of the mixing layer times the transport wind speed divided by 1000. 4. Surface wind direction is the general expected wind direction. At a specific point surface winds are highly dependent on local terrain conditions. This forecast is provided under an agreement between the Oregon Department of Agriculture and the Oregon Department of Forestry. For information contact ODA at 503-986-4701. Pete Parsons ODF Meteorologist -------------- next part -------------- An HTML attachment was scrubbed... URL: From willamette-fcst at listsmart.osl.state.or.us Wed Sep 15 11:52:52 2010 From: willamette-fcst at listsmart.osl.state.or.us (Willamette Valley Field Burning Forecast) Date: Wed, 15 Sep 2010 11:52:52 -0700 Subject: [willamette-fcst] Silverton Hills Forecast - WED, SEPTEMBER 15, 2010 Message-ID: SILVERTON HILLS FIELD BURNING FORECAST OREGON DEPARTMENT OF FORESTRY WEATHER OFFICE 12:00 PM PDT WED SEP 15, 2010 BURN ADVISORY: Agricultural burning burning is not recommended. Prep burning is allowed from now to 4:00pm. Propane flaming is allowed from now to 2:00pm. WEATHER DISCUSSION: A strengthening southwesterly flow aloft is slowly pushing a weak autumn-like cold front onshore today. Satellite imagery shows middle and high clouds spreading across most of Washington and Oregon at midday, with clouds lowering and thickening along the coastal strip. Radar is showing light rain slowly advancing to near the coastline, but there were still no reports of rain, inland over Oregon, as of late this morning. There were some sprinkles making it into northwestern Washington. The surface map continued to show weak pressure gradients across western Oregon late this morning. Southerly winds were beginning to increase from about Silverton southward across the Willamette Valley. Some sunbreaks have helped temperatures climb to near 70 degrees. Clouds should increase this afternoon along with south-southwesterly winds. Mixing heights will be slow to rise today, due to warm air aloft and the filtering of sunshine by the clouds. There could be a brief window of opportunity for open burning this afternoon, if the approaching light rain holds off until this evening and transport winds take on enough of a westerly component. It is also possible that surface winds may become too strong for good plume development later in the afternoon. Monitoring of the transport winds, via pibals, will begin at noon. TODAY'S FORECAST: Mostly cloudy. A chance of rain by late afternoon with rain likely this evening. Increasing clouds should hold high temperature in the mid 70s this afternoon. The mixing height will likely only climb to between 3000 and 4000 feet in the mid-afternoon, then drop below 3000 feet by 5 p.m. Relative humidity will drop to near 50% this afternoon with the ventilation index climbing to around 42. Silverton area sunset tonight: 7:17pm THREE-HOURLY DATA: 2pm 5pm 8pm Temperature: 74 74 65 Relative Humidity: 51% 51% 73% Surface Wind Direction: 190 210 190 Surface Wind Speed: 10 12 7 Transport Wind Direction: 200 230 200 Transport Wind Speed: 12 15 10 Estimated Mixing Height: 3500 2500 1000 Ventilation Index: 42 38 10 EXTENDED DISCUSSION: A transitory ridge should be just strong enough to provide mostly dry weather on Thursday under weak southwesterly flow aloft. If fields are dry enough, there is a possibility that transport winds will turn enough onshore to allow for open burning Thursday afternoon. Another weather system is slated to come onshore by Friday afternoon. That could also present an opening burning opportunity, Friday afternoon, if the rain holds off long enough. Wet weather is forecast this weekend...perhaps lasting into Monday. Long-range computer models are showing a potentially favorable pattern for burning, next Tuesday and Wednesday, if conditions dry out enough. EXTENDED FORECAST: Thursday: Mostly cloudy. Chance of rain. High near 75. Friday: Rain likely by the afternoon. High near 72. Saturday: Rain likely. High near 70. Sunday: Mostly cloudy. Chance of rain. High near 70. Monday: A chance of showers. High near 73. Tuesday: Partly sunny. Slight chance of showers. High near 76. Wednesday: Partly sunny. Slight chance of showers. High near 72. Notes: 1. Mixing height, as used here, is the lowest height at which the potential temperature exceeds the potential temperature at the surface. As a practical matter it is the approximate height to which a smoke plume will rise assuming good ignition, dry fuels, and winds less than about 15mph. 2. Transport winds are a layer average through the mixing height, weighted slightly toward the winds at the top of the layer. 3. Ventilation Index is the height of the mixing layer times the transport wind speed divided by 1000. 4. Surface wind direction is the general expected wind direction. At a specific point surface winds are highly dependent on local terrain conditions. This forecast is provided under an agreement between the Oregon Department of Agriculture and the Oregon Department of Forestry. For information contact ODA at 503-986-4701. Pete Parsons ODF Meteorologist -------------- next part -------------- An HTML attachment was scrubbed... URL: From willamette-fcst at listsmart.osl.state.or.us Thu Sep 16 08:57:03 2010 From: willamette-fcst at listsmart.osl.state.or.us (Willamette Valley Field Burning Forecast) Date: Thu, 16 Sep 2010 08:57:03 -0700 Subject: [willamette-fcst] willamette-fcst] Silverton Hills Forecast - Thu, September 16, 2010 Message-ID: SILVERTON HILLS FIELD BURNING FORECAST OREGON DEPARTMENT OF FORESTRY WEATHER OFFICE 9:00 AM PDT THU SEP 16, 2010 BURN ADVISORY: Agricultural burning burning is not recommended. Prep burning is not allowed. Propane flaming is not allowed. WEATHER DISCUSSION: An autumn-like cold front dropped up to one-half inch of rain in the northern Willamette Valley overnight with around one-third of an inch common as far south as Marion County. Rainfall amounts tapered off to between one-tenth and one-quarter of an inch in Linn County with less than one-tenth of an inch falling in Lane County. Rain is continuing to fall this morning along the coast and in the extreme northern Willamette Valley. Skies are cloudy across all of western Oregon. The cold front will weaken and shift slightly northward today, as a weak ridge of high pressure builds over Oregon. Not much addition rainfall is expected as far south as Marion County, but skies should remain generally cloudy with high humidity levels. TODAY'S FORECAST: Cloudy with a chance of rain...mainly in the morning. Today's high temperature should be close to yesterday's high of 74 degrees. The mixing height will climb to near 3000 feet in the mid-afternoon and top out below 4000 feet around 5 p.m. Relative humidity will likely remain above 60% all day, so damp fields will have a difficult time drying out. The ventilation index will climb to 37 by late this afternoon. Silverton area sunset tonight: 7:15pm THREE-HOURLY DATA: 11am 2pm 5pm 8pm Temperature: 66 73 74 67 Relative Humidity: 81% 64% 62% 75% Surface Wind Direction: 160 200 230 220 Surface Wind Speed: 5 6 6 2 Transport Wind Direction: 170 200 210 220 Transport Wind Speed: 4 10 10 6 Estimated Mixing Height: 1800 2500 3700 1000 Ventilation Index: 7 25 37 6 EXTENDED DISCUSSION: Another weather system is slated to come onshore Friday with rain projected to move back into the Willamette valley by midday. That makes the prospect for burning highly unlikely. Wet weather is forecast this weekend...perhaps lasting into Monday. Long-range computer models are now showing additional weather systems possibly bringing rain to the valley again Tuesday and Thursday of next week, but confidence in the forecast beyond Monday is low. EXTENDED FORECAST: Friday: Rain likely by the afternoon. High near 72. Saturday: Rain likely. High near 69. Sunday: Showers likely. High near 68. Monday: Mostly cloudy. Chance of showers. High near 70. Tuesday: Mostly cloudy. Chance of rain. High near 68. Wednesday: Partly sunny. Slight chance of showers. High near 71. Thursday: Mostly cloudy. Chance of rain. High near 70. Notes: 1. Mixing height, as used here, is the lowest height at which the potential temperature exceeds the potential temperature at the surface. As a practical matter it is the approximate height to which a smoke plume will rise assuming good ignition, dry fuels, and winds less than about 15mph. 2. Transport winds are a layer average through the mixing height, weighted slightly toward the winds at the top of the layer. 3. Ventilation Index is the height of the mixing layer times the transport wind speed divided by 1000. 4. Surface wind direction is the general expected wind direction. At a specific point surface winds are highly dependent on local terrain conditions. This forecast is provided under an agreement between the Oregon Department of Agriculture and the Oregon Department of Forestry. For information contact ODA at 503-986-4701. Pete Parsons ODF Meteorologist -------------- next part -------------- An HTML attachment was scrubbed... URL: From willamette-fcst at listsmart.osl.state.or.us Thu Sep 16 11:58:26 2010 From: willamette-fcst at listsmart.osl.state.or.us (Willamette Valley Field Burning Forecast) Date: Thu, 16 Sep 2010 11:58:26 -0700 Subject: [willamette-fcst] Silverton Hills Forecast - Thu, September 16, 2010 Message-ID: SILVERTON HILLS FIELD BURNING FORECAST OREGON DEPARTMENT OF FORESTRY WEATHER OFFICE 12:00 PM PDT THU SEP 16, 2010 BURN ADVISORY: Agricultural burning burning is not recommended. Prep burning is not allowed. Propane flaming is not allowed. WEATHER DISCUSSION: An autumn-like cold front dropped up to one-half inch of rain in the northern Willamette Valley overnight with around one-third of an inch falling as far south as Marion County. Rainfall amounts tapered off to between one-tenth and one-quarter of an inch in Linn County with less than one-tenth of an inch falling in Lane County. Rain continued to fall this morning along sections of the coast and in the extreme northern Willamette Valley. After receiving around 1.50 inches of rain overnight, Astoria, on the northern coast, has picked up an additional .40 inches this morning. Up to one-tenth of an inch of rain has fallen in the northern Willamette Valley in the past 6 hours with trance amounts falling as far south as the central valley. Skies remain cloudy across western Oregon late this morning due to a very moist southwesterly flow aloft. The cold front that has been producing the rain is forecast to shift slightly northward this afternoon, so not much addition rainfall is expected as far south as Marion County. However, cloudy skies, light winds, and high humidity levels will not aid much in the drying of damp fields. TODAY'S FORECAST: Cloudy with a chance of rain...mainly in the morning. Today's high temperature should be near 74 degrees. The mixing height will climb to near 3000 feet in the mid-afternoon and top out below 4000 feet around 5 p.m. Relative humidity will likely remain above 60% all day. The ventilation index will climb to 37 by late this afternoon. Silverton area sunset tonight: 7:15pm THREE-HOURLY DATA: 2pm 5pm 8pm Temperature: 73 74 67 Relative Humidity: 64% 62% 75% Surface Wind Direction: 200 230 220 Surface Wind Speed: 6 6 2 Transport Wind Direction: 200 210 220 Transport Wind Speed: 10 10 6 Estimated Mixing Height: 2500 3700 1000 Ventilation Index: 25 37 6 EXTENDED DISCUSSION: Another weather system is slated to come onshore Friday with rain projected to move back into the Willamette valley by early afternoon...making the prospects for burning highly unlikely. Rain should be widespread across western Oregon over the weekend, as the parent upper-level trough moves onshore. Some showers could last into Monday. Long-range computer models are now showing another, weaker, weather system possibly coming onshore Tuesday with more showers...mainly over the northern valley. The latest guidance is suggesting that a ridge will dry things out Wednesday and Thursday, which could finally allow remaining fields to dry out enough for burning. EXTENDED FORECAST: Friday: Rain likely by the afternoon. High near 72. Saturday: Rain likely. High near 69. Sunday: Showers likely. High near 68. Monday: Mostly cloudy. Chance of showers. High near 70. Tuesday: Mostly cloudy. Chance of rain north. High near 70. Wednesday: Partly sunny. High near 72. Thursday: Partly cloudy. High near 75. Notes: 1. Mixing height, as used here, is the lowest height at which the potential temperature exceeds the potential temperature at the surface. As a practical matter it is the approximate height to which a smoke plume will rise assuming good ignition, dry fuels, and winds less than about 15mph. 2. Transport winds are a layer average through the mixing height, weighted slightly toward the winds at the top of the layer. 3. Ventilation Index is the height of the mixing layer times the transport wind speed divided by 1000. 4. Surface wind direction is the general expected wind direction. At a specific point surface winds are highly dependent on local terrain conditions. This forecast is provided under an agreement between the Oregon Department of Agriculture and the Oregon Department of Forestry. For information contact ODA at 503-986-4701. Pete Parsons ODF Meteorologist -------------- next part -------------- An HTML attachment was scrubbed... URL: From willamette-fcst at listsmart.osl.state.or.us Fri Sep 17 08:59:35 2010 From: willamette-fcst at listsmart.osl.state.or.us (Willamette Valley Field Burning Forecast) Date: Fri, 17 Sep 2010 08:59:35 -0700 Subject: [willamette-fcst] Silverton Hills Forecast - FRI, SEPTEMBER 17, 2010 Message-ID: SILVERTON HILLS FIELD BURNING FORECAST OREGON DEPARTMENT OF FORESTRY WEATHER OFFICE 9:00 AM PDT FRI SEP 17, 2010 BURN ADVISORY: Recommended burn times for agricultural burning are from 12:00 p.m. to 5:00 p.m. Prep burning is not allowed. Propane flaming is not allowed. WEATHER DISCUSSION: An autumn-like weather pattern has set up across the Pacific Northwest. A strong upper-level trough is centered about 800 miles off the Oregon Coast with a very moist southwesterly flow aloft continuing to feed surges of rain into the region. Skies are cloudy across all of western Oregon this morning with radar showing an enhanced region of rain moving inland. Light rain was already making it into the northern and western Willamette Valley with light to moderate rain along the coast and over the coastal range. This area of rain will be very slow to move eastward today, with moderate to heavy rainfall totals likely from the coast range westward. Rainfall in the Willamette Valley will increase this afternoon with conditions much too damp for burning. Rainfall totals, in the Silverton Hills area, will likely range from one-quarter to one-half inch, before the rain tapers off this evening. TODAY'S FORECAST: Cloudy with a chance of rain this morning, then rain likely this afternoon. After a high temperature Thursday of 75 degrees, today's high will only climb to 72, which is 3 degrees below normal. The mixing height may briefly climb to near 3000 feet in the mid-afternoon, before increasing rain spreads across the valley. With more rain moving in and with the relative humidity likely remaining above 65% all day, fields will remain too damp for burning. The ventilation index will only climb to about 20 this afternoon. Silverton area sunset tonight: 7:13pm THREE-HOURLY DATA: 11am 2pm 5pm 8pm Temperature: 64 69 70 64 Relative Humidity: 78% 71% 68% 84% Surface Wind Direction: Var 180 190 200 Surface Wind Speed: 3 3 5 3 Transport Wind Direction: 040 190 190 200 Transport Wind Speed: 3 5 8 7 Estimated Mixing Height: 1500 2500 2000 1000 Ventilation Index: 5 13 16 7 EXTENDED DISCUSSION: Rain should be widespread across western Oregon over the weekend, as the parent upper-level trough moves onshore. Some showers could last into Monday. Long-range computer models show a weak weather system possibly bringing a few light showers to the north valley and then dry weather for Wednesday. The dry weather may not last long, with computer models showing a more active pattern late next week. It is possible that rain could hold off long enough to create a burning opportunity Thursday or Friday, but that is uncertain. EXTENDED FORECAST: Saturday: Rain likely. High near 72. Sunday: Rain turning to showers. High near 70. Monday: Mostly cloudy with some showers. High near 70. Tuesday: Mostly cloudy. Slight chance of showers north. High near 72. Wednesday: Partly sunny. High near 75. Thursday: Increasing clouds. Chance of rain late. High near 75. Friday: Chance of rain. High near 70. Notes: 1. Mixing height, as used here, is the lowest height at which the potential temperature exceeds the potential temperature at the surface. As a practical matter it is the approximate height to which a smoke plume will rise assuming good ignition, dry fuels, and winds less than about 15mph. 2. Transport winds are a layer average through the mixing height, weighted slightly toward the winds at the top of the layer. 3. Ventilation Index is the height of the mixing layer times the transport wind speed divided by 1000. 4. Surface wind direction is the general expected wind direction. At a specific point surface winds are highly dependent on local terrain conditions. This forecast is provided under an agreement between the Oregon Department of Agriculture and the Oregon Department of Forestry. For information contact ODA at 503-986-4701. Pete Parsons ODF Meteorologist -------------- next part -------------- An HTML attachment was scrubbed... URL: From willamette-fcst at listsmart.osl.state.or.us Fri Sep 17 11:56:17 2010 From: willamette-fcst at listsmart.osl.state.or.us (Willamette Valley Field Burning Forecast) Date: Fri, 17 Sep 2010 11:56:17 -0700 Subject: [willamette-fcst] Silverton Hills Forecast - Fri, September 17, 2010 Message-ID: SILVERTON HILLS FIELD BURNING FORECAST OREGON DEPARTMENT OF FORESTRY WEATHER OFFICE 12:00 PM PDT FRI SEP 17, 2010 BURN ADVISORY: Recommended burn times for agricultural burning are from now to 5:00p.m. Prep burning is not allowed. Propane flaming is not allowed. WEATHER DISCUSSION: An autumn-like weather pattern has set up across the Pacific Northwest. A strong upper-level trough is centered about 800 miles off the Oregon Coast with a very moist south-southwesterly flow aloft continuing to feed surges of rain northward across the western portion of western Oregon...mainly from the coast range westward. Skies remain cloudy across all of western Oregon late this morning, but radar shows that the main area of rain has not advanced eastward since mid-morning. Only some sprinkles or very light rain has advanced eastward into the Willamette Valley today, while the coast and coastal range has picked up between one-tenth and one-quarter of an inch in just the past 6 hours. This area of rain will be very slow to move eastward today, with locally moderate rainfall totals likely from the coast range westward. I have downgraded how much rain I think will fall today in the Willamette Valley. The Silverton Hills region will likely see some increase in the rain this afternoon, but amounts may not top one-tenth of inch, before this latest surge of moisture begins tapering off tonight. TODAY'S FORECAST: Cloudy with light rain likely spreading slowly eastward across the region this afternoon. Today's high will only climb to 72, which is 3 degrees below normal. The mixing height may briefly climb to near 3000 feet in the mid-afternoon, before increasing rain spreads across the valley. With more rain moving in and with the relative humidity likely remaining above 65% all day, fields will remain too damp for burning. The ventilation index will only climb to about 20 this afternoon. Silverton area sunset tonight: 7:13pm THREE-HOURLY DATA: 2pm 5pm 8pm Temperature: 69 70 64 Relative Humidity: 71% 68% 84% Surface Wind Direction: 180 190 200 Surface Wind Speed: 3 5 3 Transport Wind Direction: 190 190 200 Transport Wind Speed: 5 8 7 Estimated Mixing Height: 2500 2000 1000 Ventilation Index: 13 16 7 EXTENDED DISCUSSION: Rain should be widespread across western Oregon over the weekend, as the parent upper-level trough moves onshore. Some showers could last into Monday. Long-range computer models show weak weather systems possibly bringing a few light showers to the valley Tuesday and again Wednesday, but both days could easily remain dry. Any dry weather may not last long, with computer models showing a more active pattern late next week. It is possible that fields could dry out enough for a burning opportunity Thursday or Friday, if the rain holds off. That is way too far out to call at this time. EXTENDED FORECAST: Saturday: Rain likely. High near 72. Sunday: Rain turning to showers. High near 70. Monday: Mostly cloudy with some showers. High near 70. Tuesday: Mostly cloudy. Slight chance of showers north. High near 72. Wednesday: Partly sunny. Slight chance of showers. High near 74. Thursday: Increasing clouds. Chance of rain late. High near 75. Friday: Chance of light rain. High near 70. Notes: 1. Mixing height, as used here, is the lowest height at which the potential temperature exceeds the potential temperature at the surface. As a practical matter it is the approximate height to which a smoke plume will rise assuming good ignition, dry fuels, and winds less than about 15mph. 2. Transport winds are a layer average through the mixing height, weighted slightly toward the winds at the top of the layer. 3. Ventilation Index is the height of the mixing layer times the transport wind speed divided by 1000. 4. Surface wind direction is the general expected wind direction. At a specific point surface winds are highly dependent on local terrain conditions. This forecast is provided under an agreement between the Oregon Department of Agriculture and the Oregon Department of Forestry. For information contact ODA at 503-986-4701. Pete Parsons ODF Meteorologist -------------- next part -------------- An HTML attachment was scrubbed... URL: From willamette-fcst at listsmart.osl.state.or.us Mon Sep 20 08:15:00 2010 From: willamette-fcst at listsmart.osl.state.or.us (Willamette Valley Field Burning Forecast) Date: Mon, 20 Sep 2010 08:15:00 -0700 Subject: [willamette-fcst] Mon, 20 Sep 10 Message-ID: SILVERTON HILLS FIELD BURNING FORECAST OREGON DEPARTMENT OF FORESTRY WEATHER OFFICE 9:00 AM PDT MON SEP 20 2010 BURN ADVISORY: Recommended burn times for agricultural burning are from 11:00am to 5:00pm. Prep burning is allowed from 12:00pm to 5:00pm with a 50 acre limit. Propane flaming is allowed from 12:00pm to 5:00pm. WEATHER DISCUSSION: Satellite pictures this morning show solid cloud cover over western Oregon, from the coast to the Cascade crest. Rainfall amounts in the past 24 hours include .16 at the Salem Airport and .13 at the Oregon Gardens in Silverton. Upper air charts show a trough covering much of the Pacific Northwest with a significant upper level disturbence just off the southern British Columbia coast embedded in the through. This will rotate across northern Washington but be close enough to keep some showers going as far south as the mid-Willamette Valley. The morning Salem sounding showed an inversion from 4900 to 5500 feet. This will cap mixing heights today, but at a fairly high elevation above ground level. Maximum mixing height will be around 5100 feet this afternoon. The sounding also showed SSW winds near the surface veering to WSW by about 2000 feet. This is a favorable direction for open field burning. Computer models suggest smoke trajectories would be to the NE or ENE this afternoon. Finding dry fields will be the limiting factor on open field burning this afternoon. Salem's high temperature today will be near 69. Minimum relative humidity will be down to 51%. Sunset tonight: 7:08 pm THREE-HOURLY DATA: 11am 2pm 5pm 8pm Temperature: 63 68 68 60 Relative Humidity: 72% 57% 51% 64% Surface Wind Direction: 190 220 230 270 Surface Wind Speed: 11 7 7 5 Transport Wind Direction: 190 220 250 280 Transport Wind Speed: 15 10 8 5 Estimated Mixing Height: 2200 5000 5100 500 Ventilation Index: 33 50 41 2 EXTENDED DISCUSSION: The upper level trough moves east overnight tonight and weak ridging aloft should dry the area tomorrow and Wednesday. Another Pacific front moves across the area Thursday then Friday looks dry. By next weekend another major upper level trough moves across the Pacific Ocean to just off the Pacific Northwest coast to bring renewed rain to the region. EXTENDED FORECAST: Tuesday: Patchy morning fog then partly sunny, 72. SW 4-7 mph. Wednesday: Patchy morning fog then mostly sunny. SW 4-7 mph. Thursday: Patchy morning fog then mostly cloudy with a chance of rain. 73. Friday: Partly sunny, with a high near 74. Saturday: A chance of rain. Partly sunny, with a high near 73. Sunday: A chance of rain. Mostly cloudy, with a high near 72. Notes: 1. Mixing height, as used here, is the lowest height at which the potential temperature exceeds the potential temperature at the surface. As a practical matter it is the approximate height to which a smoke plume will rise assuming good ignition, dry fuels, and winds less than about 15mph. 2. Transport winds are a layer average through the mixing height, weighted slightly toward the winds at the top of the layer. 3. Ventilation Index is the height of the mixing layer times the transport wind speed divided by 1000. 4. Surface wind direction is the general expected wind direction. At a specific point surface winds are highly dependent on local terrain conditions. This forecast is provided under an agreement between the Oregon Department of Agriculture and the Oregon Department of Forestry. For information contact ODA at 503-986-4701. -------------- next part -------------- An HTML attachment was scrubbed... URL: From willamette-fcst at listsmart.osl.state.or.us Mon Sep 20 11:54:50 2010 From: willamette-fcst at listsmart.osl.state.or.us (Willamette Valley Field Burning Forecast) Date: Mon, 20 Sep 2010 11:54:50 -0700 Subject: [willamette-fcst] Mon, 20 Sep 2010 Message-ID: SILVERTON HILLS FIELD BURNING FORECAST OREGON DEPARTMENT OF FORESTRY WEATHER OFFICE 9:00 AM PDT MON SEP 20 2010 BURN ADVISORY: Recommended burn times for agricultural burning are from 11:00am to 5:00pm. Prep burning is allowed from 12:00pm to 5:00pm with a 50 acre limit. Propane flaming is allowed from 12:00pm to 5:00pm. WEATHER DISCUSSION: Satellite pictures this morning show solid cloud cover over western Oregon, from the coast to the Cascade crest. Rainfall amounts in the past 24 hours include .16 at the Salem Airport and .13 at the Oregon Gardens in Silverton. Upper air charts show a trough covering much of the Pacific Northwest with a significant upper level disturbence just off the southern British Columbia coast embedded in the through. This will rotate across northern Washington but be close enough to keep some showers going as far south as the mid-Willamette Valley. The morning Salem sounding showed an inversion from 4900 to 5500 feet. This will cap mixing heights today, but at a fairly high elevation above ground level. Maximum mixing height will be around 5100 feet this afternoon. The sounding also showed SSW winds near the surface veering to WSW by about 2000 feet. This is a favorable direction for open field burning. Computer models suggest smoke trajectories would be to the NE or ENE this afternoon. Finding dry fields will be the limiting factor on open field burning this afternoon. Salem's high temperature today will be near 69. Minimum relative humidity will be down to 51%. Sunset tonight: 7:08 pm THREE-HOURLY DATA: 11am 2pm 5pm 8pm Temperature: 63 68 68 60 Relative Humidity: 72% 57% 51% 64% Surface Wind Direction: 190 220 230 270 Surface Wind Speed: 11 7 7 5 Transport Wind Direction: 190 220 250 280 Transport Wind Speed: 15 10 8 5 Estimated Mixing Height: 2200 5000 5100 500 Ventilation Index: 33 50 41 2 EXTENDED DISCUSSION: The upper level trough moves east overnight tonight and weak ridging aloft develops over the region. Dry weather takes over as models show good agreement on the next system out in the pacific moving toward California and weakening. This may result in a few high clouds streaming across the southern Willamette Valley, otherwise fair weather will dominate aside from some night and morning fog due to the heavy recent rains. Temperatures will still be a little below late September averages as the cool air mass aloft lingers over the Pacific Northwest. The next frontal system will brush the Pacific Northwest sometime Thursday. This will not be a major rainfall event but areas of light rain are possible in the Willamette Valley. Look for drying and warming Friday into Saturday as a deep upper level low develops over the Gulf of Alaska, encouraging ridging to build over the Pacific Northwest. Eventually, however, a strengthing Pacific Jet will break through this ridge. Timing is somewhat uncertain, but Saturday night or Sunday looks like a good bet. EXTENDED FORECAST: Tuesday: Patchy morning fog then partly sunny, 72. SW 4-7 mph. Wednesday: Patchy morning fog then mostly sunny, 73. SW 4-7 mph. Thursday: Patchy morning fog then mostly cloudy with a chance of rain. 73. Friday: Partly sunny, with a high near 74. Saturday: A chance of rain late otherwise partly sunny, with a high near 73. Sunday: A chance of rain. Mostly cloudy, with a high near 72. Notes: 1. Mixing height, as used here, is the lowest height at which the potential temperature exceeds the potential temperature at the surface. As a practical matter it is the approximate height to which a smoke plume will rise assuming good ignition, dry fuels, and winds less than about 15mph. 2. Transport winds are a layer average through the mixing height, weighted slightly toward the winds at the top of the layer. 3. Ventilation Index is the height of the mixing layer times the transport wind speed divided by 1000. 4. Surface wind direction is the general expected wind direction. At a specific point surface winds are highly dependent on local terrain conditions. This forecast is provided under an agreement between the Oregon Department of Agriculture and the Oregon Department of Forestry. For information contact ODA at 503-986-4701. -------------- next part -------------- An HTML attachment was scrubbed... URL: From willamette-fcst at listsmart.osl.state.or.us Tue Sep 21 08:35:58 2010 From: willamette-fcst at listsmart.osl.state.or.us (Willamette Valley Field Burning Forecast) Date: Tue, 21 Sep 2010 08:35:58 -0700 Subject: [willamette-fcst] TUE, 21 Sep 10 Message-ID: SILVERTON HILLS FIELD BURNING FORECAST OREGON DEPARTMENT OF FORESTRY WEATHER OFFICE 9:00 AM PDT TUE SEP 21 2010 BURN ADVISORY: Recommended burn times for agricultural burning are from noon to 5:00pm. Prep burning is allowed from noon to 5:00pm with a 50 acre limit. Propane flaming is allowed from noon to 5:00pm. WEATHER DISCUSSION: Morning upper air charts show a trough to the north, over southern British Columbia and northern Washington, and another trough to the southwest, about 500 miles west of Brookings. The northern trough will pull out to the east today and the one to the southwest should push into northern California. This will leave the Willamette Valley in the middle for dry weather today and tomorrow. The morning Salem sounding showed a fairly unstable atmosphere up to above 7000 feet. There is an inversion from 7400 to 8000 feet with stable conditions above. However, daytime heating should easily push the mixing height to the inversion level and maximum mixing heights this afternoon should be about 7200 feet. Winds on the morning Salem sounding were light and variable with a tendency to northerly up to about 5000 feet. Computer models today are consistent in showing a northerly wind throughout the day today. Trajectory forecasts bring any smoke from mid Marion County into central Lane County near Eugene and Springfield. For the mid Willamette Valley today expect mostly cloudy skies this morning with some sunshine this afternoon. Winds will be light northerly becoming light northwesterly later this afternoon. Salem's high temperature today will be near 70. Relative humidity drops to 50% by 1pm. Minimum relative humidity 41%. Sunset tonight: 7:06 pm THREE-HOURLY DATA: 11am 2pm 5pm 8pm Temperature: 62 69 70 64 Relative Humidity: 65% 45% 41% 52% Surface Wind Direction: 360 340 340 300 Surface Wind Speed: 3 4 6 5 Transport Wind Direction: 010 360 360 330 Transport Wind Speed: 10 10 10 10 Estimated Mixing Height: 2800 7100 7200 500 Ventilation Index: 28 71 72 5 EXTENDED DISCUSSION: Tomorrow will be another drying day, however there likely will be areas of morning fog which may deposit some dew. Both the NAM and the GFS models are showing measurable precipitation for Thursday afternoon. Friday will see minor ridging for dry weather. Longer range, models are less pessimistic than they were earlier regarding the weekend. A deep upper low in the Pacific may remain far enough off the coast that moisture will rotate northward offshore through much of the weekend. At this point Saturday looks dry, but we will mention a possibility of rain for Sunday and Monday, but low confidence beyond Saturday. EXTENDED FORECAST: Wednesday: Areas of fog before 11am. Otherwise, partly sunny, with a high near 72. Calm wind becoming west northwest between 5 and 8 mph. Thursday: A 40 percent chance of rain after 11am. Mostly cloudy, with a high near 67. South southwest wind between 6 and 8 mph. Friday: Partly sunny, with a high near 74. Saturday: Mostly sunny, with a high near 76. Sunday: A chance of showers. Mostly cloudy, with a high near 72. Monday: A chance of rain. Mostly cloudy, with a high near 74. Notes: 1. Mixing height, as used here, is the lowest height at which the potential temperature exceeds the potential temperature at the surface. As a practical matter it is the approximate height to which a smoke plume will rise assuming good ignition, dry fuels, and winds less than about 15mph. 2. Transport winds are a layer average through the mixing height, weighted slightly toward the winds at the top of the layer. 3. Ventilation Index is the height of the mixing layer times the transport wind speed divided by 1000. 4. Surface wind direction is the general expected wind direction. At a specific point surface winds are highly dependent on local terrain conditions. This forecast is provided under an agreement between the Oregon Department of Agriculture and the Oregon Department of Forestry. For information contact ODA at 503-986-4701. -------------- next part -------------- An HTML attachment was scrubbed... URL: From willamette-fcst at listsmart.osl.state.or.us Tue Sep 21 11:55:12 2010 From: willamette-fcst at listsmart.osl.state.or.us (Willamette Valley Field Burning Forecast) Date: Tue, 21 Sep 2010 11:55:12 -0700 Subject: [willamette-fcst] Tue, 21 Sep 10 Message-ID: SILVERTON HILLS FIELD BURNING FORECAST OREGON DEPARTMENT OF FORESTRY WEATHER OFFICE 12:00 PM PDT TUE SEP 21 2010 BURN ADVISORY: Recommended burn times for agricultural burning are from noon to 5:00pm. Prep burning is allowed from noon to 5:00pm with a 50 acre limit. Propane flaming is allowed from noon to 5:00pm. WEATHER DISCUSSION: Satellite pictures show patchy mid and high level clouds streaming across the region as of late morning. These are from an upper level disturbance now off the southern Oregon coast. This will move into northern California with no further effect on mid Willamette Valley weather. The morning Salem sounding showed a fairly unstable atmosphere up to above 7000 feet. There is an inversion from 7400 to 8000 feet with stable conditions above. However, daytime heating should easily push the mixing height to the inversion level and maximum mixing heights this afternoon should be about 7200 feet. Winds on the morning Salem sounding were light and variable with a tendency to northerly up to about 5000 feet. Computer models today are consistent in showing a northerly wind throughout the day today. Trajectory forecasts bring any smoke from mid Marion County into central Lane County near Eugene and Springfield. For the mid Willamette Valley expect mostly sunny skies with a few high clouds from time to time. Winds will be light northerly becoming light northwesterly later this afternoon. Salem's high temperature today will be near 70. Relative humidity drops to 50% by 1pm. Minimum relative humidity 41%. Sunset tonight: 7:06 pm THREE-HOURLY DATA: 2pm 5pm 8pm Temperature: 64 66 60 Relative Humidity: 56% 48% 62% Surface Wind Direction: 350 350 310 Surface Wind Speed: 5 6 5 Transport Wind Direction: 360 360 330 Transport Wind Speed: 10 10 10 Estimated Mixing Height: 7100 7200 500 Ventilation Index: 71 72 5 EXTENDED DISCUSSION: Tomorrow will be another drying day, however there likely will be areas of morning fog which may deposit some dew. There has been a new run of both the NAM and GFS models since the morning forecast. The NAM model is now dry for Thursday while the GFS is still showing some precip. Friday will see minor ridging for dry weather. Longer range, models have completely backed off on precip for the weekend. Given the flip-flops we have low confidence in forecasts from Thursday on. However, if Thursday remains dry, Thursday, Friday, and Saturday all have potential for some open field burning. EXTENDED FORECAST: Wednesday: Areas of fog before 11am. Otherwise, partly sunny, with a high near 72. Calm wind becoming west northwest between 5 and 8 mph. Thursday: Mostly cloudy, slight chance of light rain, 67. SSW 6-8 mph. Friday: Partly sunny, with a high near 74. Saturday: Mostly sunny, with a high near 76. Sunday: Slight chance of showers. Mostly cloudy, with a high near 72. Monday: A chance of rain. Mostly cloudy, with a high near 74. Notes: 1. Mixing height, as used here, is the lowest height at which the potential temperature exceeds the potential temperature at the surface. As a practical matter it is the approximate height to which a smoke plume will rise assuming good ignition, dry fuels, and winds less than about 15mph. 2. Transport winds are a layer average through the mixing height, weighted slightly toward the winds at the top of the layer. 3. Ventilation Index is the height of the mixing layer times the transport wind speed divided by 1000. 4. Surface wind direction is the general expected wind direction. At a specific point surface winds are highly dependent on local terrain conditions. This forecast is provided under an agreement between the Oregon Department of Agriculture and the Oregon Department of Forestry. For information contact ODA at 503-986-4701. -------------- next part -------------- An HTML attachment was scrubbed... URL: From willamette-fcst at listsmart.osl.state.or.us Wed Sep 22 08:45:56 2010 From: willamette-fcst at listsmart.osl.state.or.us (Willamette Valley Field Burning Forecast) Date: Wed, 22 Sep 2010 08:45:56 -0700 Subject: [willamette-fcst] WED, 22 Sep 10 Message-ID: SILVERTON HILLS FIELD BURNING FORECAST OREGON DEPARTMENT OF FORESTRY WEATHER OFFICE 9:00 AM PDT WED SEP 22 2010 BURN ADVISORY: Recommended burn times for agricultural burning are from 1:00pm to 5:00pm. Prep burning is allowed from noon to 5:00pm with a 50 acre limit. Propane flaming is allowed from noon to 5:00pm. WEATHER DISCUSSION: The Willamette Valley is between an upper level trough to the south and an upper ridge to the north in an area of light winds. Satellite pictures show clouds covering most of western Oregon from the coast to the Cascade crest, but the cloud deck is quite high, quite thin, and should partially break up this afternoon. The morning Salem sounding was very similar to yesterday morning's sounding. There was a minor inversion between about 1900 and 2500 feet. This will easily mix out by late morning. There is also an unusually persistent inversion aloft with a base that has been near 7500 feet for the past couple of days. Today that inversion is between about 7800 feet and 8100 feet. Below this feature winds are light and favor northerly, above winds are westerly. Computer models indicate that lower level winds will shift to more westerly today. Gradient stacking to the east may be an issue, but smoke trajectory forecasts from the Air Resources Lab based on last night's NAM run indicate a favorable easterly direction for smoke movement later this afternoon. Gradient stacking to the east will be an issue today. Pressure gradients as of 8am included: Newport to Salem, 1.0 mb onshore; Salem to Redmond, 0.4 mb offshore. Computer models indicate an increasing onshore gradient. We will monitor the pressure pattern to see if it becomes favorable this afternoon. For the mid Willamette Valley expect mostly cloudy skies this morning, partly cloudy skies this afternoon. Temperatures will be a bit below average for this time of year and winds will switch to light westerly. Salem's high temperature today will be near 70. Relative humidity drops to 50% by 12pm. Minimum relative humidity 41%. Sunset tonight: 7:04 pm THREE-HOURLY DATA: 11am 2pm 5pm 8pm Temperature: 64 70 70 61 Relative Humidity: 60% 44% 41% 60% Surface Wind Direction: 320 260 260 260 Surface Wind Speed: 2 4 5 5 Transport Wind Direction: 270 240 240 290 Transport Wind Speed: 3 6 6 7 Estimated Mixing Height: 2400 7800 7800 1000 Ventilation Index: 7 47 47 7 EXTENDED DISCUSSION: Computer models continue to bounce back and fourth on whether tomorrow's weak weather front will produce any rain this far south. Any rainfall would be light, but there is a significant possibility that all rain from the system will stay to the north. Models are in agreement on a ridge for Friday and Saturday that will bring sunshine and warm temperatures to the region. Models are also coming into line and showing a strong low in the Gulf of Alaska late in the weekend and into the first part of next week. But the low will be far enough off the coast that moisture rotating around it will stay well west of the Pacific Northwest for fair weather and temperatures near seasonal average into early next week. EXTENDED FORECAST: Thursday: Mostly cloudy, chance of rain 66. SSW 5-10. Friday: Mostly sunny, with a high near 77. S 5. Saturday: Mostly sunny, with a high near 80. W 5. Sunday: Partly sunny, with a high near 73. W 4. Monday: Partly sunny, with a high near 78. Tuesday: Partly sunny, with a high near 75. Notes: 1. Mixing height, as used here, is the lowest height at which the potential temperature exceeds the potential temperature at the surface. As a practical matter it is the approximate height to which a smoke plume will rise assuming good ignition, dry fuels, and winds less than about 15mph. 2. Transport winds are a layer average through the mixing height, weighted slightly toward the winds at the top of the layer. 3. Ventilation Index is the height of the mixing layer times the transport wind speed divided by 1000. 4. Surface wind direction is the general expected wind direction. At a specific point surface winds are highly dependent on local terrain conditions. This forecast is provided under an agreement between the Oregon Department of Agriculture and the Oregon Department of Forestry. For information contact ODA at 503-986-4701. -------------- next part -------------- An HTML attachment was scrubbed... URL: From willamette-fcst at listsmart.osl.state.or.us Wed Sep 22 11:42:48 2010 From: willamette-fcst at listsmart.osl.state.or.us (Willamette Valley Field Burning Forecast) Date: Wed, 22 Sep 2010 11:42:48 -0700 Subject: [willamette-fcst] Wed, 22 Sep 10 Message-ID: SILVERTON HILLS FIELD BURNING FORECAST OREGON DEPARTMENT OF FORESTRY WEATHER OFFICE 12:00 PM PDT WED SEP 22 2010 BURN ADVISORY: Recommended burn times for agricultural burning are from 1:00pm to 5:00pm. Prep burning is allowed from noon to 5:00pm with a 50 acre limit. Propane flaming is allowed from noon to 5:00pm. WEATHER DISCUSSION: An upper level trough moving mainly through California is slowly pulling east with weak high pressure aloft beginning to build over the eastern Pacific Ocean. Satellite pictures as of late morning show a mixture of clouds and sun over the Willamette Valley with thicker cloud cover over the western Cascade foothills. Temperatures are running very close to where they were yesterday at the same time. The morning Salem sounding was very similar to the sounding yesterday morning. There was an unusually persistent inversion aloft with a base that has been near 7500 feet for the past couple of days. Today that inversion is between about 7800 feet and 8100 feet. Below this feature winds light light but favored northerly, above winds were westerly. The pressure gradient profile is marginally favorable at 11am. As of 11:00 am gradients included: Newport to Salem, 1.2 mb onshore; Salem to Redmond, 0.2 mb onshore Computer models indicate an increasing onshore gradient. We will monitor the pressure pattern to see if it remains favorable this afternoon. Smoke trajectory forecasts from the Air Resources Lab based on this morning's NAM run indicate a favorable easterly direction for smoke movement this afternoon. A pibal sounding is scheduled for 1:00 pm this afternoon to confirm wind direction. For the mid Willamette Valley expect partly cloudy skies this afternoon. Temperatures will be a bit below average for this time of year and winds will be light westerly. Salem's high temperature today will be near 70. Relative humidity drops to 50% by 12pm. Minimum relative humidity 41%. Sunset tonight: 7:04 pm THREE-HOURLY DATA: 2pm 5pm 8pm Temperature: 68 68 60 Relative Humidity: 47% 45% 62% Surface Wind Direction: 260 270 260 Surface Wind Speed: 4 6 5 Transport Wind Direction: 240 240 290 Transport Wind Speed: 6 6 7 Estimated Mixing Height: 7800 7800 1000 Ventilation Index: 47 47 7 EXTENDED DISCUSSION: The morning runs of both the NAM and GFS showed no rain for Salem with the weak cold front that will move through the area tomorrow. Models have been flip-flopping on this for the past couple of days. If any rain does fall it will likely be light. Models continue showing a strong low in the Gulf of Alaska late in the weekend and into the first part of next week. But the low will be far enough off the coast that moisture rotating around it will stay well west of the Pacific Northwest for fair weather and temperatures near seasonal average into early next week. EXTENDED FORECAST: Thursday: Mostly cloudy, slight chance of rain, 66. SSW 5-10. Friday: Mostly sunny, with a high near 77. S 5. Saturday: Mostly sunny, with a high near 80. W 5. Sunday: Partly sunny, with a high near 73. W 4. Monday: Partly sunny, with a high near 78. Tuesday: Partly sunny, with a high near 75. Notes: 1. Mixing height, as used here, is the lowest height at which the potential temperature exceeds the potential temperature at the surface. As a practical matter it is the approximate height to which a smoke plume will rise assuming good ignition, dry fuels, and winds less than about 15mph. 2. Transport winds are a layer average through the mixing height, weighted slightly toward the winds at the top of the layer. 3. Ventilation Index is the height of the mixing layer times the transport wind speed divided by 1000. 4. Surface wind direction is the general expected wind direction. At a specific point surface winds are highly dependent on local terrain conditions. This forecast is provided under an agreement between the Oregon Department of Agriculture and the Oregon Department of Forestry. For information contact ODA at 503-986-4701. -------------- next part -------------- An HTML attachment was scrubbed... URL: From willamette-fcst at listsmart.osl.state.or.us Thu Sep 23 08:55:15 2010 From: willamette-fcst at listsmart.osl.state.or.us (Willamette Valley Field Burning Forecast) Date: Thu, 23 Sep 2010 10:55:15 -0500 Subject: [willamette-fcst] Silverton Hills Forecast - Thu, Sep 23 2010 Message-ID: SILVERTON HILLS FIELD BURNING FORECAST OREGON DEPARTMENT OF FORESTRY WEATHER OFFICE 9:00 AM PDT THU SEP 23, 2010 BURN ADVISORY: Recommended burn times for agricultural burning are from 11:00am to 5:00pm. Prep burning is allowed from 12:00pm to 3:00pm with a 50 acre limit. Propane flaming is allowed from 12:00pm to 5:00pm. WEATHER DISCUSSION: A westerly flow aloft was pushing a warm front onshore at mid-morning. Clouds extended inland, over the Willamette Valley, to the crest of the Cascades. Light rain was falling along the coast, from Astoria to Newport, with radar showing patches of sprinkles making it over the coastal range and into the Willamette Valley. The ODA surface analysis showed weak southeasterly pressure gradients across the Willamette Valley, in response to the approaching warm front. As the warm front comes onshore, surface and transport winds should turn more southerly by early this afternoon. The warm front is forecast to weaken and lift north of the region by late in the day. Surface and transport winds are forecast to continue veering to south-southwesterly by this evening. If conditions remain dry enough, then marginally favorable conditions for open burning could materialize late this afternoon. TODAY?S FORECAST: Cloudy with sprinkles or very light rain at times, mainly north of Salem. After reaching 71 degrees on Wednesday, cloudy skies will hold maximum temperatures in the mid 60s this afternoon. The mixing height should climb above 3000 feet by late this afternoon with southerly surface and transport winds slowly veering to south-southwesterly. Relative humidity levels will likely drop below 60%, by around 2 p.m., if the bulk of the light rain falls mostly north of the district. The ventilation index should climb to near 50 late this afternoon. Silverton area sunset tonight: 7:02pm THREE-HOURLY DATA: 11am 2pm 5pm 8pm Temperature: 60 66 66 62 Relative Humidity: 67% 54% 56% 67% Surface Wind Direction: 170 180 190 220 Surface Wind Speed: 8 7 6 5 Transport Wind Direction: 180 190 210 220 Transport Wind Speed: 12 15 15 10 Estimated Mixing Height: 1800 2500 3500 1500 Ventilation Index: 22 38 52 15 EXTENDED DISCUSSION: Long-range models are continuing to show a ridge of high pressure building over the west coast beginning Friday. Skies should begin to clear Friday afternoon with temperatures warming to near normal. Winds will become very light, which ventilation conditions deteriorating. A very weak weather system is forecast to move mainly north of the state Sunday. That will increase the southwesterly transport flow over the weekend and improve ventilation conditions. The ridge is then forecast to rebuild over the region for continued dry and warm conditions through at least early next week. EXTENDED FORECAST: Friday: Patchy am fog, then mostly sunny and warmer. High near 78. Saturday: Sunny and warm. High near 83. Sunday: Partly sunny. High near 76. Monday: Mostly sunny. High near 82. Tuesday: Mostly sunny. High near 81. Wednesday: Partly sunny. High near 78. Notes: 1. Mixing height, as used here, is the lowest height at which the potential temperature exceeds the potential temperature at the surface. As a practical matter it is the approximate height to which a smoke plume will rise assuming good ignition, dry fuels, and winds less than about 15mph. 2. Transport winds are a layer average through the mixing height, weighted slightly toward the winds at the top of the layer. 3. Ventilation Index is the height of the mixing layer times the transport wind speed divided by 1000. 4. Surface wind direction is the general expected wind direction. At a specific point surface winds are highly dependent on local terrain conditions. This forecast is provided under an agreement between the Oregon Department of Agriculture and the Oregon Department of Forestry. For information contact ODA at 503-986-4701. Pete Parsons ODF Meteorologist jlwx:230910:0855 From willamette-fcst at listsmart.osl.state.or.us Thu Sep 23 11:56:33 2010 From: willamette-fcst at listsmart.osl.state.or.us (Willamette Valley Field Burning Forecast) Date: Thu, 23 Sep 2010 13:56:33 -0500 Subject: [willamette-fcst] Silverton Hills Forecast - Thu, Sep 23 2010 Message-ID: SILVERTON HILLS FIELD BURNING FORECAST OREGON DEPARTMENT OF FORESTRY WEATHER OFFICE 12:00 PM PDT THU SEP 23, 2010 BURN ADVISORY: Recommended burn times for agricultural burning are from now to 5:00pm. Prep burning is allowed from now to 3:00pm with a 50 acre limit. Propane flaming is allowed from now to 5:00pm. WEATHER DISCUSSION: A westerly flow aloft was pushing a warm front across the Willamette Valley late this morning. Radar and surface reports showed light rain extending southward to about Corvallis, with a back edge to the rainfall apparent near the coastal range. Rainfall totals through 11 a.m. were very light in the valley, with just a trace reported at the Salem Airport and only a couple hundredths of an inch from Aurora north to Portland. The main area of rain, associated with the warm, should push east of the Silverton Hills area by 2 p.m., with some drying likely later this afternoon. However, much of the region could pick up a few hundredths of an inch over the hour or two. The ODA surface analysis showed weak southerly pressure gradients across the Willamette Valley, but slightly stronger gradients along the coast. Southerly winds were gusting to around 20 mph along the north coast, late this morning, and had increased to around 10 mph in the Willamette Valley. Southerly winds should increase slightly across the Willamette Valley this afternoon and are still forecast to turn more southwesterly following the passage of the weak warm front. If conditions dry out enough this afternoon, in the wake of the warm front, transport winds and mixing heights may become marginally favorable for open burning. FORECAST FOR THE REMAINDER OF TODAY: Cloudy skies with light rain likely tapering off after about 2 p.m. Cloudy skies will hold maximum temperatures in the low to mid 60s this afternoon. The mixing height should climb above 3000 feet by late this afternoon with southerly surface and transport winds slowly veering to south-southwesterly. Relative humidity levels will not likely drop below 60%. The ventilation index should climb to near 50 late this afternoon. Silverton area sunset tonight: 7:02pm THREE-HOURLY DATA: 2pm 5pm 8pm Temperature: 62 65 62 Relative Humidity: 67% 61% 67% Surface Wind Direction: 180 190 220 Surface Wind Speed: 7 6 5 Transport Wind Direction: 190 210 220 Transport Wind Speed: 15 15 10 Estimated Mixing Height: 2500 3500 1500 Ventilation Index: 38 52 15 EXTENDED DISCUSSION: Long-range models are continuing to show a ridge of high pressure building over the west coast beginning Friday. Skies should begin to clear Friday afternoon with temperatures warming to near normal. Winds will become very light, which ventilation conditions deteriorating. A very weak weather system is forecast to move mainly north of the state Sunday. That will increase the southwesterly transport flow over the weekend and improve ventilation conditions. The ridge is then forecast to rebuild over the region for continued dry and warm conditions through at least early next week. EXTENDED FORECAST: Friday: Patchy am fog, then mostly sunny and warmer. High near 78. Saturday: Sunny and warm. High near 83. Sunday: Partly sunny. High near 76. Monday: Mostly sunny. High near 82. Tuesday: Mostly sunny. High near 81. Wednesday: Partly sunny. High near 78. Notes: 1. Mixing height, as used here, is the lowest height at which the potential temperature exceeds the potential temperature at the surface. As a practical matter it is the approximate height to which a smoke plume will rise assuming good ignition, dry fuels, and winds less than about 15mph. 2. Transport winds are a layer average through the mixing height, weighted slightly toward the winds at the top of the layer. 3. Ventilation Index is the height of the mixing layer times the transport wind speed divided by 1000. 4. Surface wind direction is the general expected wind direction. At a specific point surface winds are highly dependent on local terrain conditions. This forecast is provided under an agreement between the Oregon Department of Agriculture and the Oregon Department of Forestry. For information contact ODA at 503-986-4701. Pete Parsons ODF Meteorologist jlwx:230910:1156 From willamette-fcst at listsmart.osl.state.or.us Fri Sep 24 08:55:40 2010 From: willamette-fcst at listsmart.osl.state.or.us (Willamette Valley Field Burning Forecast) Date: Fri, 24 Sep 2010 10:55:40 -0500 Subject: [willamette-fcst] Silverton Hills Forecast - Fri, Sep 24 2010 Message-ID: SILVERTON HILLS FIELD BURNING FORECAST OREGON DEPARTMENT OF FORESTRY WEATHER OFFICE 9:00 AM PDT FRI SEP 24, 2010 BURN ADVISORY: Agricultural burning burning is not recommended. Prep burning is allowed from 12:00pm to 3:00pm with a 50 acre limit. Propane flaming is allowed from 12:00pm to 5:00pm. WEATHER DISCUSSION: A ridge of high pressure is building over the west coast. Considerable low-level moisture is left over from the warm front that passed through the region Thursday. Mostly cloudy skies cover northwestern Oregon with patchy fog in the Willamette Valley this morning. Skies should begin to clear this afternoon with temperatures warming to near normal. Light south-southwesterly transport winds will need to be monitored for the possibility of limited open burning this afternoon. TODAY?S FORECAST: Mostly cloudy this morning with areas of fog. Partly sunny this afternoon and much warmer. After reaching only 61 degrees on Thursday, today?s high will top out near 75. The mixing height should climb to around 3000 feet between 2 p.m. and 5 p.m. Surface winds will be light southerly with transport winds slowly veering to south-southwesterly at less than 10 mph. Relative humidity levels will likely drop below 50% around 2 p.m. The ventilation index will only climb to about 26 this afternoon. Silverton area sunset tonight: 7:00pm THREE-HOURLY DATA: 11am 2pm 5pm 8pm Temperature: 62 71 75 71 Relative Humidity: 72% 51% 43% 47% Surface Wind Direction: 140 210 220 280 Surface Wind Speed: 5 6 6 5 Transport Wind Direction: 180 210 220 280 Transport Wind Speed: 5 8 8 4 Estimated Mixing Height: 2000 3200 3000 1000 Ventilation Index: 10 26 24 4 EXTENDED DISCUSSION: Southwesterly flow aloft will begin to increase Saturday, as the upper-level ridge shifts east of the state. An increase in the south-southwesterly transport winds may improve ventilation enough to allow for limited open burning. A very weak weather system is forecast to move onshore Sunday, with a chance of sprinkles or very light rain making it as far south and east as the Silverton Hills region. If the area stays dry enough, there could be an open burning opportunity Sunday afternoon. The ridge is forecast to rebuild over the region Monday with another weak system possibly creating an open burning opportunity next Tuesday. The ridge is then forecast to strongly build over the state, with offshore flow possibly pushing temperatures to well above normal by Thursday. EXTENDED FORECAST: Saturday: Mostly sunny and warm. High near 81. Wind SSW 5-10. Sunday: Mostly cloudy. Chance of light rain. High near 75. Wind SW 5-10. Monday: Areas of morning fog, then mostly sunny. High near 80. Tuesday: Increasing clouds. Chance of light rain late. High near 75. Wednesday: Partly sunny. High near 78. North winds. Thursday: Sunny and very warm. High near 85. NE winds. Friday: Increasing clouds. High near 80. Notes: 1. Mixing height, as used here, is the lowest height at which the potential temperature exceeds the potential temperature at the surface. As a practical matter it is the approximate height to which a smoke plume will rise assuming good ignition, dry fuels, and winds less than about 15mph. 2. Transport winds are a layer average through the mixing height, weighted slightly toward the winds at the top of the layer. 3. Ventilation Index is the height of the mixing layer times the transport wind speed divided by 1000. 4. Surface wind direction is the general expected wind direction. At a specific point surface winds are highly dependent on local terrain conditions. This forecast is provided under an agreement between the Oregon Department of Agriculture and the Oregon Department of Forestry. For information contact ODA at 503-986-4701. Pete Parsons ODF Meteorologist jlwx:240910:0855 From willamette-fcst at listsmart.osl.state.or.us Fri Sep 24 11:57:26 2010 From: willamette-fcst at listsmart.osl.state.or.us (Willamette Valley Field Burning Forecast) Date: Fri, 24 Sep 2010 13:57:26 -0500 Subject: [willamette-fcst] Silverton Hills Forecast - Fri, Sep 24 2010 Message-ID: SILVERTON HILLS FIELD BURNING FORECAST OREGON DEPARTMENT OF FORESTRY WEATHER OFFICE 12:00 PM PDT FRI SEP 24, 2010 BURN ADVISORY: Agricultural burning burning is not recommended. Prep burning is allowed from now to 3:00pm with a 50 acre limit. Propane flaming is allowed from now to 5:00pm. WEATHER DISCUSSION: Residual low-level moisture, from the warm front that passed through the region on Thursday, led to the formation of widespread low clouds and patchy fog across northwestern Oregon this morning. The remainder of the state had mostly sunny skies. The ODA surface analysis shows very weak southerly pressure gradients across western Oregon late this morning with Willamette Valley winds generally around 5 mph or less. An upper-level ridge of high pressure is building over Oregon. Skies are slowly clearing over northwestern Oregon late this morning with further clearing expected this afternoon. Warming aloft and some sunshine will help high temperatures recover to near-normal this afternoon. Light south-southwesterly transport winds may be too light to effectively evacuate smoke from the valley and will need to be monitored this afternoon. FORECAST FOR THE REMAINDER OF TODAY: Partly sunny this afternoon with temperatures climbing into the mid 70s. The mixing height should only climb to around 3000 feet between 2 p.m. and 5 p.m. Surface winds will be light southerly with SSW transport winds at less than 10 mph. Relative humidity levels will likely drop to 50% around 3 p.m. The ventilation index will only climb to about 26 this afternoon. Silverton area sunset tonight: 7:00pm THREE-HOURLY DATA: 2pm 5pm 8pm Temperature: 70 75 69 Relative Humidity: 53% 43% 49% Surface Wind Direction: 210 220 280 Surface Wind Speed: 6 6 5 Transport Wind Direction: 210 220 280 Transport Wind Speed: 8 8 4 Estimated Mixing Height: 3200 3000 1000 Ventilation Index: 26 24 4 EXTENDED DISCUSSION: Southwesterly flow aloft will begin to increase Saturday, as the upper-level ridge shifts east of the state. An increase in the south-southwesterly transport winds may improve ventilation enough, late in the afternoon, to allow for limited open burning. A very weak weather system is forecast to move onshore Sunday, with light rain likely along the coast and in the extreme northern Willamette Valley. There is a good chance of rain as far south as the Silverton Hills region. If fields stay dry enough for burning, there is a slight chance that ventilation conditions may be sufficient for limited open burning Sunday afternoon. The ridge is forecast to rebuild over the region Monday, which would allow for the drying of damp fields. Another weak system may creat an open burning opportunity next Tuesday. The ridge is then forecast to strongly build over the state, with offshore flow possibly pushing temperatures to well above normal by Thursday. EXTENDED FORECAST: Saturday: Mostly sunny and warm. High near 81. Wind SSW 5-10. Sunday: Mostly cloudy. Chance of light rain. High near 75. Wind SW 5-10. Monday: Areas of morning fog, then mostly sunny. High near 80. Tuesday: Increasing clouds. Chance of light rain late. High near 75. Wednesday: Partly sunny. High near 78. North winds. Thursday: Sunny and very warm. High near 85. NE winds. Friday: Increasing clouds. High near 80. Notes: 1. Mixing height, as used here, is the lowest height at which the potential temperature exceeds the potential temperature at the surface. As a practical matter it is the approximate height to which a smoke plume will rise assuming good ignition, dry fuels, and winds less than about 15mph. 2. Transport winds are a layer average through the mixing height, weighted slightly toward the winds at the top of the layer. 3. Ventilation Index is the height of the mixing layer times the transport wind speed divided by 1000. 4. Surface wind direction is the general expected wind direction. At a specific point surface winds are highly dependent on local terrain conditions. This forecast is provided under an agreement between the Oregon Department of Agriculture and the Oregon Department of Forestry. For information contact ODA at 503-986-4701. Pete Parsons ODF Meteorologist jlwx:240910:1157 From willamette-fcst at listsmart.osl.state.or.us Sat Sep 25 09:05:19 2010 From: willamette-fcst at listsmart.osl.state.or.us (Willamette Valley Field Burning Forecast) Date: Sat, 25 Sep 2010 09:05:19 -0700 Subject: [willamette-fcst] Silverton Hills Forecast - SAT, SEPTEMBER 25, 2010 Message-ID: SILVERTON HILLS FIELD BURNING FORECAST OREGON DEPARTMENT OF FORESTRY WEATHER OFFICE 9:00 AM PDT SAT SEP 25, 2010 BURN ADVISORY: Agricultural burning burning is not recommended. Prep burning is not allowed. Propane flaming is not allowed. WEATHER DISCUSSION: An upper-level ridge has shifted east, to over Idaho, with increasing southwesterly flow aloft over Oregon this morning. Satellite imagery shows only patchy fog and low clouds in the Willamette Valley, which should quickly give way to sunny skies later this morning. The Salem sounding showed a surface-based temperature inversion that extended upward to about 1800 feet. That will not likely get mixed out until temperatures climb into the mid 70s early this afternoon. The air aloft is quite warm, so look for valley temperatures to climb at least into the low 80s by late this afternoon. The ODA surface analysis showed weak southeasterly pressure gradients this morning over western Oregon with valley winds generally 5 mph or less. As a weakening offshore cold front moves closer to the coastline today, southerly surface and transport winds are forecast to turn more southwesterly, which may provide adequate ventilation for limited open burning later this afternoon. TODAY'S FORECAST: Patchy morning fog, then sunny and warmer. After reaching 76 degrees on Friday, today's high will top out near 83. The mixing height will rise to 3000 feet around 2 p.m., top out near 4000 feet around 5 p.m., then quickly drop to 1500 feet by 8 p.m. Surface winds S 3-8 mph this morning, becoming SW 5-10 mph this afternoon. Transport winds S 5 mph this morning, veering to SW 12-18 mph this afternoon. Relative humidity will drop to 50% around noon and bottom out near 35% around 5 p.m. The ventilation index will climb to near 70 late this afternoon. Silverton area sunset tonight: 6:58 p.m. THREE-HOURLY DATA: 11am 2pm 5pm 8pm Temperature: 70 80 82 71 Relative Humidity: 55% 38% 34% 53% Surface Wind Direction: 170 220 230 250 Surface Wind Speed: 7 5 6 6 Transport Wind Direction: 180 200 230 240 Transport Wind Speed: 5 12 18 15 Estimated Mixing Height: 1500 2800 4000 1500 Ventilation Index: 8 34 72 22 EXTENDED DISCUSSION: A weak cold front is forecast to move onshore Sunday morning, with light rain likely along the coast and in the northern Willamette Valley. There is a good chance of rain as far south as the Silverton Hills region. The upper-level ridge is forecast to rebuild over the region Monday, with sunshine and warm temperatures helping to dry any damp fields. Another weak system may turn transport winds onshore and create an open burning opportunity next Tuesday. The ridge is then forecast to strongly build over the state for the second half of next week, with above normal temperatures. The next burning opportunity appears to be next Friday. EXTENDED FORECAST: Sunday: Mostly cloudy. Chance of light rain. High near 74. Wind SW 5-12. Monday: Areas of morning fog...mostly sunny. High near 80. Light wind. Tuesday: Increasing clouds. Chance of light rain late. High near 75. Wednesday: Partly sunny. High near 78. Thursday: Mostly sunny and warm. High near 80. Friday: Increasing clouds. High near 78. Notes: 1. Mixing height, as used here, is the lowest height at which the potential temperature exceeds the potential temperature at the surface. As a practical matter it is the approximate height to which a smoke plume will rise assuming good ignition, dry fuels, and winds less than about 15mph. 2. Transport winds are a layer average through the mixing height, weighted slightly toward the winds at the top of the layer. 3. Ventilation Index is the height of the mixing layer times the transport wind speed divided by 1000. 4. Surface wind direction is the general expected wind direction. At a specific point surface winds are highly dependent on local terrain conditions. This forecast is provided under an agreement between the Oregon Department of Agriculture and the Oregon Department of Forestry. For information contact ODA at 503-986-4701. Pete Parsons ODF Meteorologist -------------- next part -------------- An HTML attachment was scrubbed... URL: From willamette-fcst at listsmart.osl.state.or.us Mon Sep 27 08:53:24 2010 From: willamette-fcst at listsmart.osl.state.or.us (Willamette Valley Field Burning Forecast) Date: Mon, 27 Sep 2010 10:53:24 -0500 Subject: [willamette-fcst] Silverton Hills Forecast - Mon, Sep 27 2010 Message-ID: SILVERTON HILLS FIELD BURNING FORECAST OREGON DEPARTMENT OF FORESTRY WEATHER OFFICE 9:00 AM PDT MON SEP 27 2010 BURN ADVISORY: Agricultural burning burning is not recommended. Prep burning is allowed from 12:00pm to 3:00pm with a 50 acre limit. Propane flaming is allowed from 12:00pm to 5:00pm. WEATHER DISCUSSION: Upper air charts show a deep low in the northern Gulf of Alaska this morning, while an upper ridge builds over the intermountain region. This is giving a weak southwesterly flow aloft the region. Embedded in that southwesterly flow is a Pacific warm front/cold front combination. The warm front is producing clouds over most of western Washington and extreme northwestern Oregon. For the most part those clouds should stay north of Marion County, but some clouds may drift over the region during the afternoon. The cold front will move northeast and should not affect the area. The morning Salem sounding showed warming at most levels and a fairly stable atmosphere. There was an inversion from the surface to about 2800 feet. This should mix out this afternoon. We anticipate a mixing height of 3000 feet by about 1pm. Winds on the sounding were light southerly at the surface veering to light southwesterly by about 3500 feet. Unfortunately it does not look like this favorable southwesterly wind direction will be present this afternoon. Computer models are showing a shift to north-northeasterly by mid afternoon. Surface pressure gradients have already gone offshore with a pressure difference from Redmond to Newport of 2.5mb. Expect mostly sunny skies today. Salem's high temperature today will be near 84. Minimum relative humidity will be near 51%. Sunset tonight: 6:54 pm THREE-HOURLY DATA: 11am 2pm 5pm 8pm Temperature: 73 81 83 74 Relative Humidity: 71% 56% 53% 66% Surface Wind Direction: 190 240 330 330 Surface Wind Speed: 4 4 5 4 Transport Wind Direction: 180 220 020 350 Transport Wind Speed: 3 2 4 6 Estimated Mixing Height: 1200 3100 4000 500 Ventilation Index: 4 6 16 3 EXTENDED DISCUSSION: The upper ridge centered over Nevada and Utah will remain over the western US much of the week. Computer models show a transport wind over northwest Oregon from the north or northeast through Thursday, then going back to southwest by Friday. Afternoon mixing heights will likely slowly deterioriate through about Thursday as well. EXTENDED FORECAST: Tuesday: Partly sunny, with a high near 77. Calm wind becoming north between 5 and 8 mph. Wednesday: Mostly sunny, with a high near 76. North northeast wind between 6 and 9 mph. Thursday: Mostly sunny, with a high near 79. Friday: Mostly sunny, with a high near 79. Saturday: Mostly sunny, with a high near 76. Sunday: Partly sunny, with a high near 74. Notes: 1. Mixing height, as used here, is the lowest height at which the potential temperature exceeds the potential temperature at the surface. As a practical matter it is the approximate height to which a smoke plume will rise assuming good ignition, dry fuels, and winds less than about 15mph. 2. Transport winds are a layer average through the mixing height, weighted slightly toward the winds at the top of the layer. 3. Ventilation Index is the height of the mixing layer times the transport wind speed divided by 1000. 4. Surface wind direction is the general expected wind direction. At a specific point surface winds are highly dependent on local terrain conditions. This forecast is provided under an agreement between the Oregon Department of Agriculture and the Oregon Department of Forestry. For information contact ODA at 503-986-4701. jlwx:270910:0853 From willamette-fcst at listsmart.osl.state.or.us Mon Sep 27 11:43:47 2010 From: willamette-fcst at listsmart.osl.state.or.us (Willamette Valley Field Burning Forecast) Date: Mon, 27 Sep 2010 13:43:47 -0500 Subject: [willamette-fcst] Silverton Hills Forecast - Mon, Sep 27 2010 Message-ID: SILVERTON HILLS FIELD BURNING FORECAST OREGON DEPARTMENT OF FORESTRY WEATHER OFFICE 12:00PM PDT MON SEP 27 2010 BURN ADVISORY: Agricultural burning burning is not recommended. Prep burning is allowed up until 3:00pm with a 50 acre limit. Propane flaming is allowed up until 5:00pm. WEATHER DISCUSSION: Upper air charts are showing a deep low in the northern Gulf of Alaska this, while an upper ridge continues to build over the intermountain region. This is giving a weak southwesterly flow aloft the region. A weak disturbance in that flow supports a Pacific system that earlier brought clouds to parts of NW Oregon. Those clouds have now retreated into Washington and the state is nearly cloud free. The morning Salem sounding showed warming at most levels and a fairly stable atmosphere. There was an inversion from the surface to about 2800 feet. This should mix out this afternoon. We anticipate a mixing height of 3000 feet by about 1pm with a maximum mixing height of about 4000 feet this afternoon. Winds on the sounding were light southerly at the surface veering to light southwesterly by about 3500 feet. Models are still showing a transition to a northerly transport wind later this afternoon. Early afternoon pibals may continue to show the favorable SW winds, but forecast smoke trajectories from the Air Resources Lab show smoke eventually drifting southward toward central Lane County. Pressure gradients as of 11am are slightly onshore from the coast to Salem (0.3mb) but remain offshore from Redmond to Salem (1.7mb). Look for sunshine this afternoon. Salem's high temperature today will be near 84. Minimum relative humidity will be near 51%. Sunset tonight: 6:54 pm THREE-HOURLY DATA: 2pm 5pm 8pm Temperature: 81 83 74 Relative Humidity: 56% 53% 66% Surface Wind Direction: 240 330 330 Surface Wind Speed: 4 5 4 Transport Wind Direction: 220 020 350 Transport Wind Speed: 2 4 6 Estimated Mixing Height: 3100 4000 500 Ventilation Index: 6 16 3 EXTENDED DISCUSSION: The upper ridge centered over Nevada and Utah will remain over the western US much of the week. Computer models show a transport wind over northwest Oregon from the north or northeast through Thursday, then going back to southwest by Friday. Afternoon mixing heights will likely slowly deterioriate through about Thursday as well. EXTENDED FORECAST: Tuesday: Partly sunny, with a high near 77. Calm wind becoming north between 5 and 8 mph. Wednesday: Mostly sunny, with a high near 76. North northeast wind between 6 and 9 mph. Thursday: Mostly sunny, with a high near 79. Friday: Mostly sunny, with a high near 79. Saturday: Mostly sunny, with a high near 76. Sunday: Partly sunny, with a high near 74. Notes: 1. Mixing height, as used here, is the lowest height at which the potential temperature exceeds the potential temperature at the surface. As a practical matter it is the approximate height to which a smoke plume will rise assuming good ignition, dry fuels, and winds less than about 15mph. 2. Transport winds are a layer average through the mixing height, weighted slightly toward the winds at the top of the layer. 3. Ventilation Index is the height of the mixing layer times the transport wind speed divided by 1000. 4. Surface wind direction is the general expected wind direction. At a specific point surface winds are highly dependent on local terrain conditions. This forecast is provided under an agreement between the Oregon Department of Agriculture and the Oregon Department of Forestry. For information contact ODA at 503-986-4701. jlwx:270910:1143 From willamette-fcst at listsmart.osl.state.or.us Tue Sep 28 08:42:30 2010 From: willamette-fcst at listsmart.osl.state.or.us (Willamette Valley Field Burning Forecast) Date: Tue, 28 Sep 2010 10:42:30 -0500 Subject: [willamette-fcst] Silverton Hills Forecast - Tue, Sep 28 2010 Message-ID: SILVERTON HILLS FIELD BURNING FORECAST OREGON DEPARTMENT OF FORESTRY WEATHER OFFICE 9:00 AM PDT TUE SEP 28 2010 BURN ADVISORY: Recommended burn times for agricultural burning are from 1:00pm to 5:00pm. Prep burning is allowed from 3:00pm to 5:00pm with a 50 acre limit. Propane flaming is allowed from 2:00pm to 5:00pm. WEATHER DISCUSSION: A broad ridge of high pressure in the upper atmosphere covers much of the western United States this morning. The Pacific Northwest is on the edge of this ridge with a southwesterly flow aloft. That southwesterly flow is again pushing some cloudiness into western Washington and portions of northwest Oregon. This is aided by low level onshore flow from the coast to the Valley. The Newport to Salem gradient as of 8:00am was 1.3mb. There is an offshore gradient, however from Redmond to Salem. As of 8:00am Redmond's pressure was 1.1mb higher than Salem's. The morning Salem sounding showed a light westerly flow at the surface but a moderate north-northeasterly flow from about 800 feet to 3000 feet. The temperature trace showed a quite stable atmosphere over the Valley. Several shallow inversions were present from the surface to about 2500 feet. Also there was evidence of subsidence, or sinking air motion, aloft which does not allow for good smoke ventilation. Computer models show a northerly transport wind today. Smoke trajectory forecasts from the Air Resources Lab show smoke from Marion County headed south toward Lane County today. Bottom line: It does not look favorable for open field burning this afternoon. Expect patchy fog and low clouds this morning and mostly sunny skies this afternoon. Salem's high temperature today will be near 82. It will remain quite humid today with dewpoint temperatures in the low 60's. Relative humidity drops to 50% by 3pm. Minimum relative humidity 49%. Sunset tonight: 6:52 pm THREE-HOURLY DATA: 11am 2pm 5pm 8pm Temperature: 71 80 82 71 Relative Humidity: 73% 56% 49% 68% Surface Wind Direction: 360 330 350 320 Surface Wind Speed: 4 5 7 6 Transport Wind Direction: 020 360 360 020 Transport Wind Speed: 7 6 6 5 Estimated Mixing Height: 1100 2500 3200 500 Ventilation Index: 8 15 19 2 EXTENDED DISCUSSION: The northerly transport wind pattern will continue tomorrow for unfavorable burning conditions. An upper disturbance embedded in the southwesterly flow aloft will move by to the north late on Thursday which should shift the winds over the Willamette Valley. This will need to be monitored for a possible burn opportunity, however at this point it looks like the wind shift would come too late for burning. Friday remains an opportunity. EXTENDED FORECAST: Wednesday: Mostly sunny, with a high near 81. NNE 5-9 mph Thursday: Mostly sunny, with a high near 81. Wind Light/Variable becomming SW 3-6 mph during the evening. Friday: Mostly sunny, with a high near 77. Saturday: Mostly sunny, with a high near 76. Sunday: Partly sunny, with a high near 74. Sunday Night: Mostly cloudy, with a low around 51. Monday: Partly sunny, with a high near 72. Notes: 1. Mixing height, as used here, is the lowest height at which the potential temperature exceeds the potential temperature at the surface. As a practical matter it is the approximate height to which a smoke plume will rise assuming good ignition, dry fuels, and winds less than about 15mph. 2. Transport winds are a layer average through the mixing height, weighted slightly toward the winds at the top of the layer. 3. Ventilation Index is the height of the mixing layer times the transport wind speed divided by 1000. 4. Surface wind direction is the general expected wind direction. At a specific point surface winds are highly dependent on local terrain conditions. This forecast is provided under an agreement between the Oregon Department of Agriculture and the Oregon Department of Forestry. For information contact ODA at 503-986-4701. jlwx:280910:0842 From willamette-fcst at listsmart.osl.state.or.us Tue Sep 28 11:44:57 2010 From: willamette-fcst at listsmart.osl.state.or.us (Willamette Valley Field Burning Forecast) Date: Tue, 28 Sep 2010 13:44:57 -0500 Subject: [willamette-fcst] Silverton Hills Forecast - Tue, Sep 28 2010 Message-ID: SILVERTON HILLS FIELD BURNING FORECAST OREGON DEPARTMENT OF FORESTRY WEATHER OFFICE 12:00 PM PDT TUE SEP 28 2010 BURN ADVISORY: Recommended burn times for agricultural burning are from 1:00pm to 5:00pm. Prep burning is allowed from 3:00pm to 5:00pm with a 50 acre limit. Propane flaming is allowed from 2:00pm to 5:00pm. WEATHER DISCUSSION: A broad ridge of high pressure in the upper atmosphere covers much of the western United States today. The Pacific Northwest is on the edge of this ridge with a southwesterly flow aloft. That southwesterly flow is pushing some cloudiness into western Washington and portions of northwest Oregon. Satelllite pictures show the clouds beginning to break up in the Willamette Valley with moust cloudiness near the Willamette River. The morning Salem sounding showed a light westerly flow at the surface but a moderate north-northeasterly flow from about 800 feet to 3000 feet. The temperature trace showed a quite stable atmosphere over the Valley. Several shallow inversions were present from the surface to about 2500 feet. Also there was evidence of subsidence, or sinking air motion, aloft which does not allow for good smoke ventilation. Latest computer models continue toshow a northerly transport wind today. Smoke trajectory forecasts from the Air Resources Lab based on the 12Z NAM and the 15Z RUC show smoke from Marion County headed south toward Lane County today. It is unlikely that open field burning will occur today. Remaining clouds should break to reveal mostly sunny skies this afternoon. Salem's high temperature today will be near 82. It will remain quite humid today with dewpoint temperatures in the low 60's. Relative humidity drops to 50% by 3pm. Minimum relative humidity 49%. Sunset tonight: 6:52 pm THREE-HOURLY DATA: 2pm 5pm 8pm Temperature: 76 79 71 Relative Humidity: 71% 58% 73% Surface Wind Direction: 010 020 350 Surface Wind Speed: 5 6 5 Transport Wind Direction: 360 360 020 Transport Wind Speed: 6 6 5 Estimated Mixing Height: 2500 3200 500 Ventilation Index: 15 19 2 EXTENDED DISCUSSION: The northerly transport wind pattern will continue tomorrow for unfavorable burning conditions. An upper disturbance embedded in the southwesterly flow aloft will move by to the north late on Thursday which should shift the winds over the Willamette Valley. This will need to be monitored for a possible burn opportunity, however latest computer models still indicate the wind shift will come too late for burning. Friday remains an opportunity. EXTENDED FORECAST: Wednesday: Mostly sunny, with a high near 81. NNE 5-9 mph Thursday: Mostly sunny, with a high near 81. Wind Light/Variable becomming SW 3-6 mph during the evening. Friday: Mostly sunny, with a high near 77. Saturday: Mostly sunny, with a high near 76. Sunday: Partly sunny, with a high near 74. Sunday Night: Mostly cloudy, with a low around 51. Monday: Partly sunny, with a high near 72. Notes: 1. Mixing height, as used here, is the lowest height at which the potential temperature exceeds the potential temperature at the surface. As a practical matter it is the approximate height to which a smoke plume will rise assuming good ignition, dry fuels, and winds less than about 15mph. 2. Transport winds are a layer average through the mixing height, weighted slightly toward the winds at the top of the layer. 3. Ventilation Index is the height of the mixing layer times the transport wind speed divided by 1000. 4. Surface wind direction is the general expected wind direction. At a specific point surface winds are highly dependent on local terrain conditions. This forecast is provided under an agreement between the Oregon Department of Agriculture and the Oregon Department of Forestry. For information contact ODA at 503-986-4701. jlwx:280910:1144 From willamette-fcst at listsmart.osl.state.or.us Wed Sep 29 08:56:35 2010 From: willamette-fcst at listsmart.osl.state.or.us (Willamette Valley Field Burning Forecast) Date: Wed, 29 Sep 2010 10:56:35 -0500 Subject: [willamette-fcst] Silverton Hills Forecast - Wed, Sep 29 2010 Message-ID: SILVERTON HILLS FIELD BURNING FORECAST OREGON DEPARTMENT OF FORESTRY WEATHER OFFICE 9:00 AM PDT WED SEP 29, 2010 BURN ADVISORY: Recommended burn times for agricultural burning are from 1:00pm to 5:00pm. Prep burning is not allowed. Propane flaming is not allowed. WEATHER DISCUSSION: A strong upper-level ridge of high pressure remains over the Pacific Northwest this morning. Satellite imagery shows low clouds covering the western valleys of Oregon and along much of the coast. Otherwise, skies are generally sunny across the state. The morning low clouds should clear from the Willamette Valley this afternoon with temperatures climbing into the low 80s. The Salem sounding this morning showed northeasterly winds below about 3000 feet with weak westerly flow aloft. Warm air aloft will cap mixing heights near or below 3000 feet this afternoon. A surface thermal trough is forecast to slowly build into southwestern Oregon today, which will maintain northeasterly transport winds. That pattern is not conducive to open burning. TODAY?S FORECAST: Morning low clouds, then mostly sunny and warm. After reaching 83 degrees on Wednesday, today?s high will top out near 81. The mixing height will only rise to about 2800 feet this afternoon, then quickly drop to around 1000 feet by 8 p.m. Surface winds N to NE 5-10 mph. Transport winds NE near 10 mph. Relative humidity will drop to 50% around 3 p.m. and bottom out near 46% around 5 p.m. The ventilation index will climb to near 34 this afternoon. Silverton area sunset tonight: 6:50 p.m. THREE-HOURLY DATA: 11am 2pm 5pm 8pm Temperature: 67 76 81 72 Relative Humidity: 73% 56% 46% 61% Surface Wind Direction: 010 010 030 050 Surface Wind Speed: 7 8 9 4 Transport Wind Direction: 030 020 010 020 Transport Wind Speed: 10 10 12 8 Estimated Mixing Height: 1800 2800 2800 1000 Ventilation Index: 18 28 34 8 EXTENDED DISCUSSION: The upper-level ridge is forecast to shift eastward, to over Idaho, on Thursday, with slowly increasing southwesterly flow aloft. The surface thermal trough will likely shift inland, by the afternoon, with transport winds becoming northerly. It is unlikely that winds will turn enough onshore to allow for open burning Thursday afternoon. By Friday, the thermal trough is forecast to progress east of the Cascades with transport winds possibly turning enough onshore to create a burning opportunity. The first significant weather system is not forecast to come onshore until Sunday. EXTENDED FORECAST: Thursday: Sunny, with a high near 84. Wind: N 5-10 mph. Friday: Patchy morning fog, then mostly sunny. High near 78. Saturday: Mostly sunny, with a high near 77. Sunday: Increasing clouds. Chance of rain late. High near 74. Monday: A chance of showers. Mostly cloudy, with a high near 72. Tuesday: Partly sunny, with a high near 72. Notes: 1. Mixing height, as used here, is the lowest height at which the potential temperature exceeds the potential temperature at the surface. As a practical matter it is the approximate height to which a smoke plume will rise assuming good ignition, dry fuels, and winds less than about 15mph. 2. Transport winds are a layer average through the mixing height, weighted slightly toward the winds at the top of the layer. 3. Ventilation Index is the height of the mixing layer times the transport wind speed divided by 1000. 4. Surface wind direction is the general expected wind direction. At a specific point surface winds are highly dependent on local terrain conditions. This forecast is provided under an agreement between the Oregon Department of Agriculture and the Oregon Department of Forestry. For information contact ODA at 503-986-4701. Pete Parsons ODF Meteorologist jlwx:290910:0856 From willamette-fcst at listsmart.osl.state.or.us Wed Sep 29 09:04:26 2010 From: willamette-fcst at listsmart.osl.state.or.us (Willamette Valley Field Burning Forecast) Date: Wed, 29 Sep 2010 11:04:26 -0500 Subject: [willamette-fcst] Silverton Hills Forecast - Wed, Sep 29 2010 Message-ID: SILVERTON HILLS FIELD BURNING FORECAST OREGON DEPARTMENT OF FORESTRY WEATHER OFFICE 9:00 AM PDT WED SEP 29, 2010 ?Corrected wording in Today?s forecast? BURN ADVISORY: Recommended burn times for agricultural burning are from 1:00pm to 5:00pm. Prep burning is not allowed. Propane flaming is not allowed. WEATHER DISCUSSION: A strong upper-level ridge of high pressure remains over the Pacific Northwest this morning. Satellite imagery shows low clouds covering the western valleys of Oregon and along much of the coast. Otherwise, skies are generally sunny across the state. The morning low clouds should clear from the Willamette Valley this afternoon with temperatures climbing into the low 80s. The Salem sounding this morning showed northeasterly winds below about 3000 feet with weak westerly flow aloft. Warm air aloft will cap mixing heights near or below 3000 feet this afternoon. A surface thermal trough is forecast to slowly build into southwestern Oregon today, which will maintain northeasterly transport winds. That pattern is not conducive to open burning. TODAY?S FORECAST: Morning low clouds, then mostly sunny and warm. After reaching 83 degrees on Tuesday, today?s high will top out near 81. The mixing height will rise to only about 2800 feet this afternoon, then drop to around 1000 feet by 8 p.m. Surface winds N to NE 5-10 mph. Transport winds NE near 10 mph. Relative humidity will drop to 50% around 3 p.m. and bottom out near 46% around 5 p.m. The ventilation index will climb to near 34 this afternoon. Silverton area sunset tonight: 6:50 p.m. THREE-HOURLY DATA: 11am 2pm 5pm 8pm Temperature: 67 76 81 72 Relative Humidity: 73% 56% 46% 61% Surface Wind Direction: 010 010 030 050 Surface Wind Speed: 7 8 9 4 Transport Wind Direction: 030 020 010 020 Transport Wind Speed: 10 10 12 8 Estimated Mixing Height: 1800 2800 2800 1000 Ventilation Index: 18 28 34 8 EXTENDED DISCUSSION: The upper-level ridge is forecast to shift eastward, to over Idaho, on Thursday, with slowly increasing southwesterly flow aloft. The surface thermal trough will likely shift inland, by the afternoon, with transport winds becoming northerly. It is unlikely that winds will turn enough onshore to allow for open burning Thursday afternoon. By Friday, the thermal trough is forecast to progress east of the Cascades with transport winds possibly turning enough onshore to create a burning opportunity. The first significant weather system is not forecast to come onshore until Sunday. EXTENDED FORECAST: Thursday: Sunny, with a high near 84. Wind: N 5-10 mph. Friday: Patchy morning fog, then mostly sunny. High near 78. Saturday: Mostly sunny, with a high near 77. Sunday: Increasing clouds. Chance of rain late. High near 74. Monday: A chance of showers. Mostly cloudy, with a high near 72. Tuesday: Partly sunny, with a high near 72. Notes: 1. Mixing height, as used here, is the lowest height at which the potential temperature exceeds the potential temperature at the surface. As a practical matter it is the approximate height to which a smoke plume will rise assuming good ignition, dry fuels, and winds less than about 15mph. 2. Transport winds are a layer average through the mixing height, weighted slightly toward the winds at the top of the layer. 3. Ventilation Index is the height of the mixing layer times the transport wind speed divided by 1000. 4. Surface wind direction is the general expected wind direction. At a specific point surface winds are highly dependent on local terrain conditions. This forecast is provided under an agreement between the Oregon Department of Agriculture and the Oregon Department of Forestry. For information contact ODA at 503-986-4701. Pete Parsons ODF Meteorologist jlwx:290910:0904 From willamette-fcst at listsmart.osl.state.or.us Wed Sep 29 11:57:26 2010 From: willamette-fcst at listsmart.osl.state.or.us (Willamette Valley Field Burning Forecast) Date: Wed, 29 Sep 2010 13:57:26 -0500 Subject: [willamette-fcst] Silverton Hills Forecast - Wed, Sep 29 2010 Message-ID: SILVERTON HILLS FIELD BURNING FORECAST OREGON DEPARTMENT OF FORESTRY WEATHER OFFICE 12:00 PM PDT WED SEP 29, 2010 BURN ADVISORY: Recommended burn times for agricultural burning are from 1:00pm to 5:00pm. Prep burning is not allowed. Propane flaming is not allowed. WEATHER DISCUSSION: A strong upper-level ridge of high pressure remains over the Pacific Northwest this morning. Satellite imagery shows low clouds continuing to blanket much of the Willamette Valley, and extending south into Douglas County, at midday. Skies were sunny across the remainder of the state. Even with some sunshine later this afternoon, warm air aloft will cap mixing heights below 3000 feet. A surface thermal trough is building into southwestern Oregon, which is resulting in northeasterly transport winds. This pattern is not conducive to open burning. TODAY?S FORECAST: Low clouds will slowly give way to sunshine this afternoon with temperatures climbing to near 80 degrees. The mixing height will remain below 2000 feet until surface temperatures warm into the mid 70s. The maximum mixing height will likely remain just below 3000 feet. Surface and transport winds will be N-NE 8-14 mph this afternoon. Relative humidity will drop to 50% around 3 p.m. and bottom out near 46% around 5 p.m. The ventilation index will climb to near 34 this afternoon. Silverton area sunset tonight: 6:50 p.m. THREE-HOURLY DATA: 2pm 5pm 8pm Temperature: 72 79 71 Relative Humidity: 57% 46% 57% Surface Wind Direction: 010 030 030 Surface Wind Speed: 8 9 4 Transport Wind Direction: 010 010 020 Transport Wind Speed: 10 12 8 Estimated Mixing Height: 2000 2800 1000 Ventilation Index: 20 34 8 EXTENDED DISCUSSION: The upper-level ridge is forecast to shift eastward, to over eastern Oregon and western Idaho, on Thursday. The surface thermal trough will likely shift into the Willamette Valley. Ventilation conditions are expected to be poor with light northerly transport winds and low mixing heights. By Friday, the thermal trough is forecast to progress east of the Cascades with transport winds possibly turning enough onshore to create a burning opportunity. Weak onshore flow is forecast for Saturday with a weather system significantly increasing the onshore flow and possibly bringing some rainfall Sunday. EXTENDED FORECAST: Thursday: Sunny, with a high near 84. Wind: N 5-10 mph. Friday: Patchy morning fog, then mostly sunny. High near 78. Saturday: Mostly sunny, with a high near 77. Sunday: Increasing clouds. Chance of rain late. High near 74. Monday: A chance of showers. Mostly cloudy, with a high near 72. Tuesday: Partly sunny, with a high near 72. Notes: 1. Mixing height, as used here, is the lowest height at which the potential temperature exceeds the potential temperature at the surface. As a practical matter it is the approximate height to which a smoke plume will rise assuming good ignition, dry fuels, and winds less than about 15mph. 2. Transport winds are a layer average through the mixing height, weighted slightly toward the winds at the top of the layer. 3. Ventilation Index is the height of the mixing layer times the transport wind speed divided by 1000. 4. Surface wind direction is the general expected wind direction. At a specific point surface winds are highly dependent on local terrain conditions. This forecast is provided under an agreement between the Oregon Department of Agriculture and the Oregon Department of Forestry. For information contact ODA at 503-986-4701. Pete Parsons ODF Meteorologist jlwx:290910:1157 From willamette-fcst at listsmart.osl.state.or.us Thu Sep 30 08:56:53 2010 From: willamette-fcst at listsmart.osl.state.or.us (Willamette Valley Field Burning Forecast) Date: Thu, 30 Sep 2010 10:56:53 -0500 Subject: [willamette-fcst] Silverton Hills Forecast - Thu, Sep 30 2010 Message-ID: SILVERTON HILLS FIELD BURNING FORECAST OREGON DEPARTMENT OF FORESTRY WEATHER OFFICE 9:00 AM PDT THU SEP 30, 2010 BURN ADVISORY: Agricultural burning burning is not recommended. Prep burning is not allowed. Propane flaming is not allowed. WEATHER DISCUSSION: The strong upper-level ridge of high pressure over the Pacific Northwest is slowly shifting eastward. The ridge axis is forecast extend from northern Nevada, through eastern Oregon and Washington, into eastern British Columbia by this afternoon. The ODA surface analysis showed a strong thermal trough extending northward along the Oregon coast with light offshore flow across western Oregon. Satellite imagery showed some low clouds over mainly the southern Willamette Valley, with far less extensive coverage than yesterday morning. Only patchy low clouds were evident in the Silverton Hills area. Otherwise, skies are generally sunny across the state this morning. The Salem sounding this morning showed further warming aloft. Mixing heights will be greatly suppressed today, likely topping out at or below 2500 feet this afternoon. Low-level winds continue to be northeasterly with weak southwesterly flow aloft. That pattern is not conducive to open burning. TODAY?S FORECAST: Patchy morning low clouds, then sunny and unseasonably warm. After reaching 76 degrees on Wednesday, more sunshine will help today?s high temperature top out near 85. The mixing height will rise to only about 2300 feet this afternoon, before quickly dropping below 1000 feet by 8 p.m. Surface and transport winds N to NE 5-10 mph, becoming light this evening. Relative humidity will drop to 50% around 1 p.m. and bottom out near 37% around 5 p.m. The ventilation index will climb to only 16 this afternoon. Silverton area sunset tonight: 6:49 p.m. THREE-HOURLY DATA: 11am 2pm 5pm 8pm Temperature: 69 81 85 76 Relative Humidity: 63% 44% 37% 50% Surface Wind Direction: 020 360 020 280 Surface Wind Speed: 5 7 7 3 Transport Wind Direction: 030 010 010 290 Transport Wind Speed: 8 7 7 4 Estimated Mixing Height: 1700 2100 2300 500 Ventilation Index: 14 15 16 2 EXTENDED DISCUSSION: The upper-level ridge will continue to shift eastward and weaken over the next few days. By tomorrow, increasing southwesterly flow aloft is forecast to shift the thermal trough east of the Cascades. That will turn transport winds onshore and cool the air aloft slightly. South-southwesterly transport winds and slightly higher mixing heights could provide adequate ventilation for limited open burning by Friday afternoon. Low-level transport winds are forecast to become north-northwesterly on Saturday, before turning strongly onshore Sunday. A cold front will likely bring some showers into the region Sunday night and Monday. The ridge is forecast to rebuild over the region Tuesday and Wednesday with dry weather and mostly northerly transport winds. EXTENDED FORECAST: Friday: Partly sunny with patchy AM fog. High near 79. Wind SW 5-10. Saturday: Morning clouds, then partly sunny. High near 75. Sunday: Increasing clouds. Chance of rain late. High near 72. Monday: Light rain turning to showers. High near 67. Tuesday: Partly sunny, with a high near 72. Wednesday: Mostly sunny, with a high near 72 Notes: 1. Mixing height, as used here, is the lowest height at which the potential temperature exceeds the potential temperature at the surface. As a practical matter it is the approximate height to which a smoke plume will rise assuming good ignition, dry fuels, and winds less than about 15mph. 2. Transport winds are a layer average through the mixing height, weighted slightly toward the winds at the top of the layer. 3. Ventilation Index is the height of the mixing layer times the transport wind speed divided by 1000. 4. Surface wind direction is the general expected wind direction. At a specific point surface winds are highly dependent on local terrain conditions. This forecast is provided under an agreement between the Oregon Department of Agriculture and the Oregon Department of Forestry. For information contact ODA at 503-986-4701. Pete Parsons ODF Meteorologist jlwx:300910:0856 From willamette-fcst at listsmart.osl.state.or.us Thu Sep 30 11:55:51 2010 From: willamette-fcst at listsmart.osl.state.or.us (Willamette Valley Field Burning Forecast) Date: Thu, 30 Sep 2010 13:55:51 -0500 Subject: [willamette-fcst] Silverton Hills Forecast - Thu, Sep 30 2010 Message-ID: SILVERTON HILLS FIELD BURNING FORECAST OREGON DEPARTMENT OF FORESTRY WEATHER OFFICE 12:00 PM PDT THU SEP 30, 2010 ?Last Forecast for the 2010 Field-Burning Season? ?This Product is Scheduled to Resume in June, 2011? BURN ADVISORY: Agricultural burning burning is not recommended. Prep burning is not allowed. Propane flaming is not allowed. WEATHER DISCUSSION: The strong upper-level ridge of high pressure over the Pacific Northwest is slowly shifting eastward. The ridge axis is forecast extend from northern Nevada, through eastern Oregon and Washington, into eastern British Columbia by this afternoon. The ODA surface analysis showed a strong thermal trough extending northward along the Oregon coast with light offshore flow across western Oregon. Midday satellite imagery still showed some low clouds over the southern Willamette Valley, but skies were sunny over the remainder of the state. The Salem sounding this morning showed further warming aloft. Mixing heights will be greatly suppressed today, likely topping out at or below 2500 feet this afternoon. Low-level winds continue to be northeasterly with weak southwesterly flow aloft. That pattern is not conducive to open burning. TODAY?S FORECAST: Sunny and unseasonably warm. Today?s high temperature will top out near 85. The mixing height will rise to only about 2300 feet this afternoon, before quickly dropping below 1000 feet by 8 p.m. Surface and transport winds N to NE 5-10 mph, becoming light this evening. Relative humidity will drop to 50% around 1 p.m. and bottom out near 37% around 5 p.m. The ventilation index will climb to only 16 this afternoon. Silverton area sunset tonight: 6:49 p.m. THREE-HOURLY DATA: 2pm 5pm 8pm Temperature: 81 85 76 Relative Humidity: 44% 37% 50% Surface Wind Direction: 360 020 280 Surface Wind Speed: 7 7 3 Transport Wind Direction: 010 010 290 Transport Wind Speed: 7 7 4 Estimated Mixing Height: 2100 2300 500 Ventilation Index: 15 16 2 EXTENDED DISCUSSION: The upper-level ridge will continue to shift eastward and weaken over the next few days. By tomorrow, increasing southwesterly flow aloft is forecast to shift the thermal trough east of the Cascades. That will turn transport winds onshore and cool the air aloft slightly. South-southwesterly transport winds and slightly higher mixing heights could provide adequate ventilation for limited open burning by Friday afternoon. Low-level transport winds are forecast to become north-northwesterly on Saturday, before turning strongly onshore Sunday. A cold front will likely bring some showers into the region Sunday night and Monday. The ridge is forecast to rebuild over the region Tuesday and Wednesday with dry weather and mostly northerly transport winds. EXTENDED FORECAST: Friday: Partly sunny with patchy AM fog. High near 79. Wind SW 5-10. Saturday: Morning clouds, then partly sunny. High near 75. Sunday: Increasing clouds. Chance of rain late. High near 72. Monday: Light rain turning to showers. High near 67. Tuesday: Partly sunny, with a high near 72. Wednesday: Mostly sunny, with a high near 72 Notes: 1. Mixing height, as used here, is the lowest height at which the potential temperature exceeds the potential temperature at the surface. As a practical matter it is the approximate height to which a smoke plume will rise assuming good ignition, dry fuels, and winds less than about 15mph. 2. Transport winds are a layer average through the mixing height, weighted slightly toward the winds at the top of the layer. 3. Ventilation Index is the height of the mixing layer times the transport wind speed divided by 1000. 4. Surface wind direction is the general expected wind direction. At a specific point surface winds are highly dependent on local terrain conditions. This forecast is provided under an agreement between the Oregon Department of Agriculture and the Oregon Department of Forestry. For information contact ODA at 503-986-4701. Pete Parsons ODF Meteorologist jlwx:300910:1155