[willamette-fcst] Forecast - Thursday, August 20th, 2009
Willamette Valley Ag/Burning Forecast
willamette-fcst at listsmart.osl.state.or.us
Thu Aug 20 09:01:39 PDT 2009
Daily Smoke Management Forecast
Oregon Department of Agriculture
Smoke Management Program
Weather Outlook and Field Burning Advisory for Willamette Valley Growers and Fire Districts.
Thursday, August 20th, 2009 at 9:00am.
Agricultural burning is not recommended.
Preparatory burning is not allowed.
Propane flaming is allowed from 11:00am until 5:00pm.
Stack burning is not allowed.
Daily high temperature records were broken Wednesday
afternoon in Portland (97 degrees), Salem (99 degrees), and
Eugene (101 degrees). The combination of high temperatures
and low humidities put the valley into State Fire Marshal
Conditions during the mid-to-late afternoon period Wednesday.
The strong ridge of high pressure that brought the record
warmth has moved east and was centered over western Idaho
this morning. Increasing south-southwesterly flow aloft
allowed a minor intrusion of cooler marine air into the
Willamette Valley overnight. Temperatures cooled into the
50s across most of the valley, and some marine low clouds
were even able to penetrate into the extreme north and
extreme south valley. Satellite imagery showed a solid
blanket of low clouds along both the Washington and Oregon
coastlines...poised to be driven inland by increasing
The mid-morning ODA surface analysis showed the thermal
trough had shifted east, into central Oregon...extending
back into southwestern Oregon. The Willamette Valley had
weak southwesterly gradients. Onshore flow will increase
today...cooling valley temperatures back closer to normal
and greatly improving ventilation conditions over western
Oregon. That should allow for open burning this afternoon,
with a significant surge of marine air forecast to invade
western Oregon with low clouds and cooler temperatures tonight.
SW 5-10 this morning, W 5-12 this afternoon.
SW 8 this morning, WSW 10 this afternoon.
Atmospheric Ventilation Conditions:
Maximum mixing height today will be near 4500 feet. Ventilation index 45.
Salem\'s high temperature today will be near 85.
Relative humidity drops to 50% by 12pm.
Minimum relative humidity will be near 37%.
Salem sunset tonight: 8:10pm; sunrise tomorrow: 6:22am.
Increasing southwesterly flow aloft, and onshore flow at the
surface, will continue the cooling trend across western
Oregon on Friday. The influx of marine tonight will be
strong enough overnight to make open burning unlikely Friday
(due to gradient-stacking), but not impossible, as the
transport wind directions will remain favorable, and another
surge of marine air is expected Friday night. A weak trough
is forecast to maintain a deep marine layer over western
Oregon Saturday, with continued southwesterly flow aloft.
Varying degrees of onshore flow will continue Sunday through
Wednesday with little to no rainfall and seasonal temperatures.
Tomorrow (21 Aug): Am Clouds...Partly Sunny in the Afternoon. 54/80
Sat (22 Aug): AM Clouds...Partly Sunny in the Afternoon. 53/79
Sun (23 Aug): AM Clouds. PM Sunshine. 51/80
Mon (24 Aug): AM Clouds...PM Sunshine. 52/84
Tue (25 Aug): AM Clouds...Partly Sunny. 53/81
Wed (26 Aug): AM Clouds...Partly Sunny. 54/82
Thu (27 Aug): AM Clouds...Partly Sunny. 54/84
weather at oda.state.or.us
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