[willamette-fcst] Forecast - Thursday, September 11th, 2008
Willamette Valley Ag/Burning Forecast
willamette-fcst at listsmart.osl.state.or.us
Thu Sep 11 09:11:52 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 9:00am.
...State Fire Marshal conditions will likely be reached 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.
The upper-level ridge of high pressure, that has been
centered offshore for the past several days, will move over
Oregon today. That will further strengthen the surface
thermal trough, along the Oregon Coast. Valley temperatures
should warm to near 90 degrees, under sunny skies, with
continued offshore flow.
The northern and central coastline will also have sunshine,
warm temperatures, and offshore flow. Low-level winds had turned
onshore along the south coast this morning, and that onshore flow
will advance northward, along the coast, this afternoon and evening,
as the surface themal trough shifts inland.
The Salem sounding showed much warmer air aloft this morning, and
a strong low-level temperature inversion, due to the building
upper-level ridge of high pressure over the state. That will keep
mixing heights at or below about 2000 feet until surface temperatures
climb into the mid 80s this afternoon. By that time, low humidities]
and increasing north-northeasterly surface winds will likely put much
of the valley into State Fire Marshal Conditions. Open burning is
highly unlikely today.
The thermal trough 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 5-12 this morning, NNE 10-17 G25 south this afternoon.
NNE 15 this morning, 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 21%.
Salem sunset tonight: 7:29pm; sunrise tomorrow: 6:48am.
A weak upper-level disturbance is forecast to flatten the
ridge, as it slide 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 burning opportunity Friday afternoon...especially
in the north valley. This system is unlikely to be strong
enough to create a burning opportunity for the south
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 forcast to turn northerly
Saturday, with highs in the low to mid 80s, and offshore by
Sunday, as temperatures warm to near 90. The ridge is
forecast to remain in place through at least Monday with low
mixing heights and northerly transport winds severly
A weak southwesterly flow aloft is forecast to advance the
surface thermal trough into Eastern Oregon around
Tuesday...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 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): Sunny and Slightly Cooler. 55/86
Wed (17 Sep): Sunny and a Little Cooler. 51/83
Thu (18 Sep): Mostly Sunny with a Continued Cooling Trend. 50/79
weather at oda.state.or.us
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