From willamette-fcst at listsmart.osl.state.or.us Thu Jun 27 15:30:44 2013 From: willamette-fcst at listsmart.osl.state.or.us (Willamette Valley Field Burning Forecast) Date: Thu, 27 Jun 2013 15:30:44 -0700 Subject: [willamette-fcst] Test Silverton Hills AM Forecast.doc Message-ID: DO NOT USE . . Test FORECAST . . DO NOT USE . . Test FORECAST SILVERTON HILLS FIELD BURNING FORECAST OREGON DEPARTMENT OF FORESTRY WEATHER OFFICE 8:50 AM PDT MON JUL 8, 2013 BURN ADVISORY: Recommended burn times for agricultural burning are 8:00 a.m. until 4:30 p.m. Prep burning is not allowed. WEATHER DISCUSSION: An upper-level ridge will continue to bring sunny and hot weather to the Willamette Valley today. Southerly flow aloft and daytime heating may produce enough instability for isolated afternoon thunderstorm development over the Cascades. At the surface, a thermal trough will remain over western Oregon with generally light offshore low-level winds. The combination of warm temperatures and low humidity will likely put the valley into State Fire Marshal Burn-Ban Conditions again this afternoon. TODAY'S FORECAST: Sunny and hot. Salem's high temperature today will be near 99 degrees (normal is 80). Relative humidity: Dropping below 30% by 2 p.m. Surface winds: NE 5-10 mph throughout the day. Transport winds: NE 10 mph throughout the day. Mixing height: Rising to near 3000 feet this afternoon. Salem's sunset tonight: 9:01 p.m. (Salem Airport data for Sunday, July 7th: High 97?F; Rainfall .00") (Maximum Ventilation index expected today: 30) EXTENDED DISCUSSION: The strong upper-level ridge is forecast break down on Tuesday, which should bring a few degrees of cooling but no significant change in mixing heights or transport winds. On Wednesday, increasing southwesterly flow aloft will force the surface thermal trough east of the Cascades. The resulting "marine push" will significantly cool temperatures and could create a burning opportunity Wednesday afternoon. Mixing heights should climb above 4000 feet with increasing westerly transport winds. Thursday and Friday will be much cooler with morning clouds giving way to partly sunny skies in the afternoon. Significant gradient-stacking will likely inhibit open burning, especially on Thursday. The National Weather Service's digital forecast is available at: http://forecast.weather.gov/MapClick.php?lat=44.90549606158295&lon=-122.8106689453125&site=pqr&unit=0&lg=en&FcstType=text 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 (ft) times the transport wind speed (mph) 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: