[willamette-fcst] Forecast - Thursday, July 12th, 2007
Willamette Valley Ag/Burning Forecast
willamette-fcst at listsmart.osl.state.or.us
Thu Jul 12 12:01:56 PDT 2007
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, July 12th, 2007 at 12:00pm.
Agricultural burning is allowed. Suggested burn times are from now until 6:00pm.
Preparatory burning is allowed from now until 2:00pm with a 100 acre limit.
Propane flaming is allowed from now until 6:00pm.
Straw stack burning is allowed from now until 6:00pm.
The strong upper-level ridge over the Pacific Northwest is
moving slowly eastward and was centered over Idaho late this
morning. South to Southeasterly flow aloft is increasing
over Oregon which brought a line of clouds and a few light
showers northward up the Willamette early this morning.
That area of cloudiness and sprinkles extended from Western
Washington to NE Oregon late this morning, with mostly sunny
skies over Western Oregon.
The morning ODA surface analysis showed that the surface
thermal trough had progressed east of the Cascades, allowing
for a very weak onshore flow in the Willamette Valley.
Tempertures will only be slightly cooler today due to the
very weak onshore flow, mostly sunny skies, and continued
very warm air aloft. Another weather disturbance, in the
upper-level flow, will move north through the Willamette
Valley tonight and Friday morning. That will likely produce
scattered showers and some thunderstorms.
W 5-10 this afternoon.
WSW 8 this afternoon.
Atmospheric Ventilation Conditions:
Maximum mixing height today will be near 4500 feet. Ventilation index 36.
Salem\'s high temperature today will be near 89.
Relative humidity droped to 49% at 11am.
Minimum relative humidity will be near 34%.
Salem sunset tonight: 8:58pm; sunrise tomorrow: 5:38am.
The upper-level flow will become southwesterly Friday
afternoon, which should end the thunderstorm threat west of
the Cascades and slightly increase the onshore surface flow
of marine air into the Willamette Valley. That will cool
high temperatures a few more degrees. The onshore flow will
still be weak, and this situation will be monitored for a
possible afternoon burning opportunity.
Weak onshore flow will continue on Saturday, with mostly
sunny skies and a touch more cooling in the Willamette
Valley. A stronger upper-level low pressure area will
approach the Pacific Coast Saturday night and swing a weak
cold front into Washington and NW Oregon on Sunday. That
system may not produce any rain, but it will further
strengthen the onshore gradients across Oregon. That will
result in the intrusion of enough marine air into the
Willamette Valley for morning low clouds and drop
temperatures to near or below normal.
A strengthening southwesterly flow aloft will develop over
Oregon on Monday. We will be closely watching surface
gradients for a possible burn opportunity either Monday or
Tuesday, ahead of the next weather system, which is forecast
to move onto the coastline sometime Tuesday. The long-range
computer models do not agree on the location nor strength of
this system. It may move onshore and bring showers to much
of the region Wednesday and Thursday or stay far enough
offshore to keep us dry and fairly warm. My forecast
reflects this system moving onshore late Tuesday through
Thursday, but my confidence is this forecast beyond Monday
Tomorrow (13 Jul): Chance of Morning Thundershowers. Partly Sunny and Cooler Afternoon. 60/85
Sat (14 Jul): Partly Cloudy. 57/83
Sun (15 Jul): Morning Clouds. Afternoon Clearing. 55/77
Mon (16 Jul): Morning Clouds. Afternoon Clearing. 52/79
Tue (17 Jul): Increasing Clouds with a Chance of Showers Late. 54/75
Wed (18 Jul): Mostly Cloudy. Chance of Showers. 52/72
Thu (19 Jul): Mostly Cloudy. Chance of Showers. 50/72
weather at oda.state.or.us
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