[willamette-fcst] Forecast - Thursday, September 11th, 2008
Willamette Valley Ag/Burning Forecast
willamette-fcst at listsmart.osl.state.or.us
Thu Sep 11 11:14:05 PDT 2008
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, September 11th, 2008 at 12:00pm.
...State Fire Marshal conditions are likely this afternoon, due to low
humidities and increasing north-northeasterly winds...
Agricultural burning is not recommended.
Preparatory burning is not allowed.
Propane flaming is not allowed.
Stack burning is not allowed.
An upper-level ridge of high pressure, centered offshore for the past several
days, is moving over Oregon today. The late-morning ODA surface analysis showed
a broad surface thermal trough along the Oregon Coast. North-northeasterly
gradients were producing sunny skies and offshore winds across most of Western
Oregon. The lone exception was along the south coast, where onshore flow was
producing foggy and cool conditions.
Valley temperatures, along with the northern and central coast, had climbed into
the low to mid 70s by late this morning with sunny skies. Relative humidities,
in the valley, were already near 30%, so State Fire Marshal conditions will
likely be met this afternoon, where surface winds are 15 mph or greater.
Meanwhile, on the south coast, Brookings was a foggy 50 degrees.
Onshore flow will advance northward, along the coast, this evening, as the
surface thermal trough slowly shifts inland. It is forecast to shift east of
the Cascades overnight with a little marine air beginning to seep into the
Willamette Valley by Friday morning. Low clouds will spread northward along
the coastline overnight with little or no inland penetration by Friday morning.
NNE 7-17 G20 this afternoon.
NE 15 this afternoon.
Atmospheric Ventilation Conditions:
Maximum mixing height today will be near 3400 feet. Ventilation index 51.
Salem\'s high temperature today will be near 90.
Minimum relative humidity will be near 23%.
Salem sunset tonight: 7:29pm; sunrise tomorrow: 6:48am.
A weak upper-level disturbance is forecast to flatten the ridge, as it slides
across Southern British Columbia Friday afternoon. That will push the surface
thermal trough into Eastern Oregon and induce weak onshore flow into Western
Oregon. Temperatures will cool slightly with the transport winds backing from
northeasterly to northwesterly. That may create a brief burning opportunity,
Friday afternoon, for extreme north valley fields, but transport winds are
forecast to stay northerly south of Salem.
A strong upper-level ridge is forecast to build over the Pacific Northwest this
weekend for sunny and warmer weather. Surface and transport winds are forecast
to turn northerly Saturday. By Sunday, the transport winds will turn offshore,
with temperatures warming into the low 90s. The ridge is forecast to remain in
place through at least Monday with low mixing heights and northerly transport
winds severly limiting burning opportunities.
A weak South-southwesterly flow aloft is forecast, beginning Tuesday, with a slight
chance of mainly mountain thunderstorms, from a weak upper-level low pressure
system off the Northern California Coast. The surface thermal trough will shift
into Eastern Oregon...initiating a slow cooling trend across Western Oregon.
That may create open burning opportunities, or at least improve ventilation
conditions enough for some prep burning, Tuesday afternoon through Thursday.
Tomorrow (12 Sep): Mostly Sunny but Cooler with Increasing Onshore Flow. 52/84
Sat (13 Sep): Sunny and Warmer. North Winds. 49/84
Sun (14 Sep): Sunny and Very Warm. Northeast Winds. 55/92
Mon (15 Sep): Mostly Sunny and Continued Very Warm. 57/92
Tue (16 Sep): Mostly Sunny. Slightly Cooler. 55/86
Wed (17 Sep): Partly Cloudy. 51/83
Thu (18 Sep): Partly Cloudy. 50/79
weather at oda.state.or.us
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