[willamette-fcst] Forecast - Friday, January 23rd, 2009
Willamette Valley Ag/Burning Forecast
willamette-fcst at listsmart.osl.state.or.us
Fri Jan 23 09:01:10 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.
Issued:
Friday, January 23rd, 2009 at 9:00am.
Burn Advisory:
Agricultural burning is not recommended.
Stack burning is not allowed.
Weather Discussion:
A dry and cold northerly flow aloft is developing across
British Columbia with a mild and moist southerly flow aloft
over California this morning. The two, very different,
upper-level flow patterns converge over Washington and
Oregon with lots of clouds but really nothing in the way of
precipitation across the region. Mostly cloudy skies kept
temperatures warmer overnight across Oregon, with Willamette
Valley minimums generally in the low 30s. Hillsboro was one
of the coldest spots with a low of 29 degrees. Cloudy skies
helped to keep fog from forming west of the Cascades, but
fog covered many of the valleys in central and eastern
Oregon. Temperatures east of the Cascades were also more
moderate overnight, where minumums were mostly in the 20s
and low 30s.
Infrared satellite imagery showed lots of mid-level and some
high clouds hanging out over Oregon, with weak flow aloft
not moving the clouds anywhere quickly. The ODA surface
analysis showed cold Canadian air beginning to spill into
eastern Washington, which was increasing the offshore
pressure gradients through the Columbia Gorge. Easterly
winds were gusting over 30 mph at Troutdale and to 60 mph in
Corbett. Easterly winds had also increased slightly along
the coast, compared with yesterday morning. Light northerly
winds were developing in the Willamette Valley.
The Salem sounding this morning continued to show a fairly
strong temperature inversion from the surface up to about
2000 feet with the temperature remaining fairly constant
from 2000 feet up to about 5000 feet. The freezing level
held fairly steady over the past 24 hours and was at 7600
feet. However, the air mass did cool a few more degrees
below 5000 feet, compared with Thursday, so mixing heights
should be slightly higher today. However, conditions remain
too stagnant to allow for stack burning.
Considerable middle and high clouds will remain over the
region today, with not much of a chance of any precipitation
statewide. With a lack of fog across western Oregon, there
will also be some sunbreaks today. High temperatures will
climb into the mid to upper 40s across the Willamette Valley
this afternoon. Increasing cool outflow, from the Columbia
Gorge, should keep north valley temperatures from climbing
above the mid 40s. Downsloping easterly winds will help the
coastline shoot into the 50s this afternoon, except near
Astoria, where cold low-level easterly winds may keep
temperatures in the 40s.
Surface Winds:
N 0-8 this morning, N 5-10 this afternoon.
Transport Winds:
N 8 this morning, N 10 this afternoon.
Atmospheric Ventilation Conditions:
Maximum mixing height today will be near 1200 feet. Ventilation index 12.
High Temperature:
Salem\'s high temperature today will be near 47.
Humidities:
Minimum relative humidity will be near 56%.
Sunrise/Sunset:
Salem sunset tonight: 5:08pm; sunrise tomorrow: 7:40am.
Extended Outlook:
The cold northerly flow over British Columbia will sag south
over Washington and Oregon this weekend. That will lower
snow levels to 4000 feet Saturday and to near 2000 feet
Saturday night, but moisture will be very limited. Colder
Arctic air will spill into Washington late Saturday and into
northern Oregon Sunday morning, lowering the snow level to
the valley floors west of the Cascades. The air mass will
rapidly dry out, as the colder air moves south across the
Willamette Valley Sunday afternoon and evening. There may
be a brief period of flurries of light snow with the onset
of the colder air, but significant accumulations are
unlikely.
Temperatures should start out in the upper 30s or low 40s
Sunday, then hold steady or fall during the day, as the
modified Arctic air moves south across the Willamette
Valley. Skies should begin to clear Sunday night, with dry
and cold northerly winds dropping valley temperatures well
into the 20s, and perhaps the upper teens. Monday should
become mostly sunny, as cold Canadian high pressure settles
over the area. High temperatures will struggle into the low
to mid 30s, with temperatures in the Columbia Gorge staying
near of below freezing. Brisk easterly winds will continue
at the western end of the Gorge with cold northerly winds in
the Willamette Valley.
After a cold night Monday night, with valley minimums
dropping back well into the 20s, clouds will increase
Tuesday in response to a weak weather system sliding by
mainly to our north. It could be storng enough to bring
some light precipitation to northern Oregon late Tuesday.
Precipitation from this system would likely fall as snow, in
the Columbia Gorge, and perhaps briefly in the northern
Willamette Valley, before changing to rain. Precipitation
totals shouuld be very light, but some minor snow
accumulations are possible in the mountains and in the
Columbia Gorge.
A few sprinkles may persist across northwestern Oregon, as
high pressure builds back over the region Wednesday
afternoon through Thursday. A more westerly jet stream is
forecast to bring a series of wet weather systems onshore
beginning late Friday. These systems should bring rain to
the lowlands and snow to the mountains.
Tomorrow (24 Jan): Chance of Showers. Snow Level dropping to 2000 Feet Late. 32/45
Sun (25 Jan): Light Rain Turning to Light Snow...Colder. Little or No Accumulations. 32/38
Mon (26 Jan): Mostly Sunny and Cold. 23/35
Tue (27 Jan): Increasing Clouds. Chance of Light Rain of Snow Late. 22/38
Wed (28 Jan): Mostly Cloudy. Chance of Sprinkles. 29/41
Thu (29 Jan): Areas of AM Fog. Mostly Cloudy. Chance of Sprinkles North. 35/47
Fri (30 Jan): Increasing Clouds. Chance of Rain Late. 35/50
ODA Meteorologist
weather at oda.state.or.us
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