[willamette-fcst] Forecast - Friday, February 20th, 2009
Willamette Valley Ag/Burning Forecast
willamette-fcst at listsmart.osl.state.or.us
Fri Feb 20 09:02:55 PST 2009
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, February 20th, 2009 at 9:00am.
Agricultural burning is not recommended.
Stack burning is not allowed.
Fair skies and light winds overnight, once again, allowed
most Willamette Valley temperatures to drop below freezing.
Hillsboro dipped to 26 degrees, Corvallis dropped to 28
degrees and Eugene fell to 29. Salem dropped to 30 and
Portland 31. Minimums along the coast were in the mid 30s.
Considerable middle and high clouds continued to cover much
of Oregon. In addition, areas of fog and low clouds formed
in sections of the valley this morning...mainly from Salem
south to Eugene.
A nearly stationary upper-level low pressure center
continues to sit and spin, well off the northern California
coastline, with a warming southwesterly flow aloft over
Oregon and Washington. The freezing level has steadily
risen over the past few days and jumped above 8000 feet
yesterday. The upper-level ridge axis is slowly shifting
eastward, and the freezing level over Salem slipped back to
7000 feet this morning. Satellite imagery showed bands of
middle and high clouds circulating northward over Oregon
this morning, but shower activity remained well offshore.
Warm air aloft will keep mixing heights at or below about
1500 feet again today. Transport winds were measured over
Salem this morning as light southeasterly and are expected
to become light north-northeasterly this afternoon. Stack
burning is not allowed, again, today.
The ODA surface analysis showed weaker offshore pressure
gradients across western Oregon this morning, compared with
yesterday. Easterly winds were only blowing up to about 10
mph along the coast. Winds in the Willamette Valley were
generally calm. Like yesterday, there will be considerable
middle and high clouds filtering the late-winter sunshine
this afternoon. Willamette Valley temperatures should range
from the low 50s in the south valley, where to fog will take
time to break up, to the upper 50s in areas of the north
valley. Coastal temperatures may locally reach the low 60s,
like they did yesterday at Tillamook, where the high was 63
degrees. Surface winds will remain lightly offshore.
Var 0-5 this morning, NE 3-7 this afternoon.
SE 5 this morning, NNE 7 this afternoon.
Atmospheric Ventilation Conditions:
Maximum mixing height today will be near 1500 feet. Ventilation index 11.
Salem\'s high temperature today will be near 57.
Minimum relative humidity will be near 49%.
Salem sunset tonight: 5:48pm; sunrise tomorrow: 7:03am.
Middle and high cloudiness should increase over Oregon
Saturday, as an offshore weather system slowly moves towards
the coastline. The flow aloft will turn more southerly with
offshore surface gradients increasing. The chance of rain
will increase significantly by Saturday night, especially
over southwestern Oregon.
Areas of rain will likely spread across western Oregon by
Sunday with wouth-wouthweseterly flow aloft keeping snow
levels above the Cascade passes. Valley temperatures will
remain mild with southerly surface winds improving
ventilation conditions. As the offshore upper-level low
pressure system approaches the coastline Monday, colder air
aloft should drop the snow level down to the Cascade passes
with increasing valley rain and mountain snow.
The upper-level trough is forecast to come onshore Tuesday,
with continued showers and snow levels dropping to about
3000 feet. Showers will likely taper off some on Wednesday
with the flow aloft becoming northwesterly and drying out.
A cool weather system is forecast to dive into the region,
from the Gulf of Alaska, on Thursday, increasing the chance
of showers again.
Tomorrow (21 Feb): Areas of AM Fog. Mostly Cloudy and Mild. Chance of Rain Late. 32/55
Sun (22 Feb): Rain Likely. Snow Level 5-6000 Feet. 38/53
Mon (23 Feb): Rain Likely at Times. Snow Level 5000 Feet...Dropping late. 40/50
Tue (24 Feb): Showers. Mountain Snow. Snow Level 3000 Feet. 38/50
Wed (25 Feb): Decreasing Showers. Snow Level 3000 Feet. 37/49
Thu (26 Feb): Chance of Showers. Snow Level 3000 Feet. 35/49
Fri (27 Feb): Showers Likely. Snow Level 2-3000 Feet. 35/49
weather at oda.state.or.us
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