[willamette-fcst] Forecast - Thursday, July 17th, 2008
Willamette Valley Ag/Burning Forecast
willamette-fcst at listsmart.osl.state.or.us
Thu Jul 17 08:10:19 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, July 17th, 2008 at 9:00am.
Agricultural burning is not recommended.
Preparatory burning is not allowed.
Propane flaming is allowed from 2:00pm until 5:00pm.
Stack burning is not allowed.
A weak upper-level disturbance moved across Washington
Wednesday and increased the westerly flow aloft over Oregon.
That brought some marine air into Western Oregon with
Wednesday temperatures about 10 degrees cooler than on
Tuesday. Willamette Valley highs were in the low 80s.
Transport wind speeds were not sufficient to allow for open
Onshore flow continued overnight with low clouds blanketing
the coastline. Visible satellite imagery showed low clouds
had moved into Western Washington and the extreme Northern
Willamette Valley this morning. Patchy low clouds had also
spilled into the south valley around Eugene. The remainder
of the state had mostly sunny skies. Temperatures started
out a few degrees cooler today across the Willamette Valley
with minimums ranging from 46 at Eugene to 55 in Portland.
The morning ODA surface analysis showed high pressure
building into Western Washington and Western Oregon with a
weak thermal trough extending from Eastern Washington
Central Oregon and into SW Oregon. Western Oregon had
onshore flow with some gradiant-stacking and significant
The Salem sounding this morning showed very slight cooling
below about 8000 feet, due to increasing onshore flow, and
slight warming aloft, due to a weak transitory upper-level
ridge. Winds were generally northwesterly except for an
area of northeast winds from 1-3000 feet. Winds at that
level are forecast to turn northerly by midday, much as they
Another weak upper-level trough is forecast to drop into
extreme Southern British Columbia late this afternoon and
move across Washington early Friday morning. That will
maintain the onshore flow across Western Oregon today, which
will likely cap afternoon temperatures near 80 degrees in
the valley. Skies will be sunny, except for areas of low
clouds in the extreme north and south valley this morning.
Northwesterly surface and transport winds should increase
this afternoon, due to the combination of the sea-breeze
effect and the approaching weak upper-level trough. Surface
winds may approach or locally exceed 15 mph late this later
this afternoon, which could limit burning opportunities.
Transport wind speeds may be a little stronger than they
were Wednesday. However, daytime heating will need to
alleviate the gradient-stacking and Medford-Draw issues to
insure good ventilation conditions for open burning. All of
these weather factors will be closely monitored today with
pibal readings starting at 1pm.
NW 5-10 this morning, NW 8-15 this afternoon.
NE 7 this morning, NNW 9 this afternoon.
Atmospheric Ventilation Conditions:
Maximum mixing height today will be near 5000 feet. Ventilation index 45.
Salem\'s high temperature today will be near 80.
Relative humidity drops to 50% by 12pm.
Minimum relative humidity will be near 34%.
Salem sunset tonight: 8:54pm; sunrise tomorrow: 5:43am.
An upper-level trough should increase the onshore flow
enough for areas of drizzle, Friday morning, along the coast
and western slopes of the coast range. Low clouds should
penetrate inland, across most of the Willamette Valley,
Friday morning. As high pressure begins to rebuild over
Oregon, skies will clear with transport winds turning more
northerly Friday afternoon. The upper-level ridge will
strengthen Saturday with northerly transport winds and
temperatures warming to normal.
The long-range computer models have been very inconsistent
in their handling of a weak upper-level low pressure area slated
to move onshore around Sunday afternoon. At east some
clouds are likely from this system. There is also a slight
chance of a shower or thunershower, especially over and near
the Cascades, Sunday afternoon and night.
A westerly flow aloft is forecast Monday through Thursday
with possible troughs strong enough to bring a light showers
Tomorrow (18 Jul): Morning Clouds...Mostly Sunny Afternoon. Wind: NNW 10-20 mph. 50/79
Sat (19 Jul): Mostly Sunny and Warmer. Wind: N 10-20 mph. 49/84
Sun (20 Jul): Partly Cloudy. Slight Chance of a Shower/T-Storm Late. 52/81
Mon (21 Jul): Slight Chance AM Shower. Partly Sunny. 55/78
Tue (22 Jul): Mostly Cloudy. Slight Chance of Showers. 54/75
Wed (23 Jul): Morning Clouds...Sunny & Warmer. 52/80
Thu (24 Jul): Mostly Sunny and Warmer. 53/84
weather at oda.state.or.us
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