[willamette-fcst] Forecast - Wednesday, September 24th, 2008
Willamette Valley Ag/Burning Forecast
willamette-fcst at listsmart.osl.state.or.us
Wed Sep 24 08:03:13 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.
Wednesday, September 24th, 2008 at 9:00am.
Agricultural burning is not recommended.
Preparatory burning is not allowed.
Propane flaming is not allowed.
Stack burning is not allowed.
A warm front was bringing some light rain to portions of NW
Washington this morning, while Western Oregon was enjoying a
touch of sunshine. A weakening cold front, less than 200
miles offshore, will move onshore this evening...likely
spreading some light rain inland across the Willamette
Valley. High temperatures should climb into the upper 60s,
ahead of the cold front, this afternoon.
The ODA surface analysis showed low pressure offshore and
high pressure over the Southern Oregon Coast combining to
create south-southeasterly gradients across the Willamette
Valley. Gradients should turn more southerly and increase
later this afternoon. Ventilation conditions may provide a
burning opportunity this afternoon. However, transport winds
may be to brisk and/or to southerly to allow for burning.
The Salem sounding this morning showed south-southwesterly
transport winds and fairly warm air aloft. Some cooling
aloft is forecast by early this afternoon, which may combine
with surface heating to raise mixing heights to 3000 feet.
If the cooling aloft does not occur in time, mixing heights
may also be a limiting factor for any burning today. We
will begin pibal readings at 11am to monitor the transport winds.
The cold front is forecast to sweep across the Willamette
Valley tonight. Rainfall amounts with this system do not
look overly imperssive and may not exceed one-tenth of an
inch for much of the valley...especially south.
S 5-15 this morning, SW 10-20 this afternoon.
S 15 this morning, SSW 20 this afternoon.
Atmospheric Ventilation Conditions:
Maximum mixing height today will be near 3000 feet. Ventilation index 60.
Salem\'s high temperature today will be near 68.
Minimum relative humidity will be near 47%.
Salem sunset tonight: 7:05pm; sunrise tomorrow: 7:03am.
An upper-level trough should maintain a little shower
activity through Thursday...mainly in the north valley. The
bulk of the rain from this storm is forecast to stay north
of Oregon with total rainfall amounts of about one-tenth of
an inch projected to fall in the Nothern Willamette Valley
and possibly less in the south valley. If the south valley
happens to stay dry enough, transport winds may become
favorable for burning there Thursday, as the upper-level
trough passes by to the north.
A weak upper-level trough is forecast to turn the flow aloft
southwesterly Friday and may create a late-afternoon burning
opportunity for dry fields. The system will move into
Southern British Columbia early Saturday with the bulk of
the precipitation forcast to stay north of Oregon. There
may be a light shower in the extreme north valley Saturday
morning, but the odds favor dry weather. Depending on the
timing and strength of that system, it may also create a
burning opportunity Saturday. That is too far out to call
at this time.
The long-range models are still forecasting an upper-level
ridge to amplify, just east of the region Sunday, putting
Western Oregon under weak southwesterly flow aloft with
possible offshore flow at the surface. The ridge is
forecast to slowly slide eastward, early next week, with a
series of weather systems coming onshore about mid-week.
This transition may bring another burning opportunity,
although the transport winds may be to southerly. It
appears that a parade of increasingly wet systems will move
onshore late next week, which would mark the end of the 2008
Thu (25 Sep): Mostly Cloudy North with a Chance of Showers. Partly Sunny South. 52/67
Fri (26 Sep): Mostly Sunny. 45/75
Sat (27 Sep): Partly Sunny. Slight Chance of a Shower Extreme North Valley. 47/73
Sun (28 Sep): Sunny and Warm. 47/80
Mon (29 Sep): Mostly Sunny and Warm. 48/80
Tue (30 Sep): Increasing Clouds. Chance of Rain Late. 50/73
Wed (01 Oct): Light Rain Likely. 48/66
weather at oda.state.or.us
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