[willamette-fcst] Forecast - Friday, August 15th, 2008
Willamette Valley Ag/Burning Forecast
willamette-fcst at listsmart.osl.state.or.us
Fri Aug 15 08:03:11 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.
Friday, August 15th, 2008 at 9:00am.
...State Fire Marshal Conditions will likely be met this afternoon...
Agricultural burning is not recommended.
Preparatory burning is not allowed.
Propane flaming is not allowed.
Stack burning is not allowed.
A strong upper-level ridge of high pressure brought record
high temperatures to the interior of Western Oregon
Thursday. State Fire Marshal conditions were met by 3pm
Thursday over most of the valley due to high temperatures
and low humidities. Much of the Willamette Valley reached
100 degrees or better with Portland, Hillsboro, and Eugene
hitting daily records. Medford also tied their daily record
high of 108 degrees, set in 1933. Salem hit 100 degrees
Thursday, but that was not a record for the date. Corvallis
was the valley cool spot with a maximum of 99 degrees.
The following records were tied or broken Thursday in the
Location High Pervious Record
Portland (Downtown) 101 97 set in 1942
Portland (Airport) 102 97 set in 1967
Hillsboro (Airport) 101 100 set in 1933
Eugene (Airport) 100 (tied) 100 set in 2002
The upper-level ridge had shifted over Eastern Washington
and Eastern Oregon this morning with increasing southerly
flow aloft feeding middle and high clouds over the western
half of both states, along with the return of California
wildfire smoke to much of Western Oregon. A weak
upper-level disturbance was rotaing northward offshore and
Doppler radar was showing shower activity just off the
coast. The showers are not expected to make it inland but a
few sprinkles could clip the coastal region today.
The ODA surface analysis showed a strong thermal trough over
the interior valleys of Western Oregon with low pressure
centers near Portland and Medford. A high pressure center
was near North Bend, along the southern coast. A weak
influx of marine air was making it though the southern
coastal gaps into Corvallis and Eugene, where temperatures
had cooled into the low 60s. The north valley did not see
any marine air overnight with minimums in the mid to upper 60s.
Satellite imagery showed mostly clear skies from the
Cascades eastward across Oregon and Idaho. To the west,
coastal low clouds and fog blanketed the coastline this
morning, in reponse to onshore flow induced by the thermal
trough over western valleys. Some low clouds were
penetrating into the coastal mountain gaps but none had made
it into the Willamette Valley.
The Salem sounding this morning showed very warm air aloft
with easterly winds from near the surface up to 10,000 feet.
A strong subsidence inversion had been created by the
upper-level ridge and will cap mixing heights near 2000 feet
today. In addition to poor ventilation conditions, State
Fire Marshal Conditions will likely be met again this
afternoon over much of the valley, especially north, due to
high temperatures and low humidities.
The upper-level ridge will hold fast today with record warm
temperatures expected in the western valleys again this
afternoon...especially from Salem north. The south valley
will likely be a few degrees cooler due to the weak influx
of marine air this morning. Low clouds and fog will keep
the immediate coastline cool today with highs there only in
the 60s. The onshore flow may turn enough northerly along
the extreme north coast to clear skies there this
afternoon...allowing temperatures to climb into the 70s.
Light southerly flow aloft will continue to feed middle and
high clouds over the region tonight with temperatures, once
again, not dipping below 60 across most of the valley.
Var 5-10 north...SW 5-15 south this morning, N 5-10 north...NW 5-15 south this afternoon.
NE 10 north...W 10 south this morning, N 10 north...NW10 south this afternoon.
Atmospheric Ventilation Conditions:
Maximum mixing height today will be near 2300 feet. Ventilation index 23.
Salem\'s high temperature today will be near 100.
Relative humidity drops to 50% by 11am.
Minimum relative humidity will be near 24%.
Salem sunset tonight: 8:17pm; sunrise tomorrow: 6:16am.
An upper-level disturbance is forecast to move close enough
tothe coastline Saturday to bring a threat of showers or
thundershowers to the western half of Oregon...especially
the Southern Cascades. It will be another scorcher will
most valley highs over the century mark for the third
straight day. There is a pretty good chance of showers or
thundershowers rolling off the Cascades and over the
Willamette Valley Saturday evening and/or night.
The upper-level ridge is forecast to shift to over Western
Montana Sunday. Increasing southerly flow aloft will spread
more mid and high-level moisture across Oregon with the
chance of showers or thundershowers spreading eastward
across the state. The thermal trough is forecast to finally
shift east of the Cascades which will begin a cooling trend
for Western Oregon.
The flow aloft will turn southwesterly by Monday afternoon,
which will stabilize the air mass and push the thundershower
threat east of the region. It will also increase the
onshore flow and bring a significant cool-down to Western
Oregon. A weak cold front may be strong enough to produce
some light showers along the coast and the Willamette Valley.
A stronger system is still forecast to move onshore Tuesday
afternoon or night for another chance of light rain across
Western Oregon. Depending on the strength and timing of
this system, it may create a burning upportunity ahead of
it. The valley will have a good chance of showers Wednesday
with the passing of a stronger upper-level trough. The flow
aloft is forecast to turn northwesterly and begin drying out Thursday.
Tomorrow (16 Aug): Sunny and Hot. Chance of T-Storms Late. 64/102
Sun (17 Aug): Mostly Cloudy. Chance of T-Storms. 62/92
Mon (18 Aug): Chance of AM T-Storms...Cooler with a Chance of Showers. 58/74
Tue (19 Aug): Partly Cloudy. Increasing Clouds Late with a Chance of Light Rain. 53/80
Wed (20 Aug): Chance of Showers and Cooler. 55/74
Thu (21 Aug): Mostly Cloudy. Slight Chance of Showers. 52/74
Fri (22 Aug): Morning Clouds...Afternoon Clearing. 50/78
weather at oda.state.or.us
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