[willamette-fcst] Willamette Valley Forecast
Willamette Valley Ag/Burning Forecast
willamette-fcst at listsmart.osl.state.or.us
Fri Dec 11 09:55:15 PST 2009
Oregon Department of Agriculture
Smoke Management Program
Weather Outlook and Field Burning Advisory for Willamette
Valley Growers and Fire Districts.
Friday, December 11th, 2009 at 9:00am.
Agricultural burning is not recommended.
Stack burning is not allowed.
A very cold and dry air mass remains entrenched
Washington and Oregon this morning. Clear skies
temperatures to drop into the teens, and locally
digits, in the Willamette Valley this morning, with
areas only a couple of degrees warmer than on
morning. Skies also remained clear along the
central coast, with most morning temperatures
the low to mid 20s and locally into the upper teens.
areas east of the Cascades fell below zero again
As expected, some significant changes in the weather
are taking place this morning. The flow aloft over
has become westerly, with a weather system
offshore ridge of high pressure and moving into
That has continued to warm the air aloft, between
10,000 feet, with a shallow layer of above-freeezing
showing up on the morning soundings, over Salem and
between 2000 and about 5000 feet. The column of
freezing air was thicker over Medford than over
Temperatures were still well below freezing from the
up to about 2000 feet over both locations. That
the stage for a wintry mix of precipitation later
through Saturday, as the feed of moisture moves
across western Oregon.
Clouds spread northward, into southern Oregon,
and Doppler radar was showing precipitation also
north of the California border at mid-morning. Rain
falling in Brookings, on the southern Oregon Coast,
temperatures had warmed into the upper 30s. Surface
temperatures in the southwestern interior were still
20s, where the precipitation will fall in the form
wintry mix as it spreads northward this morning.
Computer models differ considerably on both their
intensity of the precipitation, as it moves
across western Oregon today. Some begin the wintry
the southern Willamette Valley, as early as
with precipitation likely moving into the south
this evening. The plume of moisture will sweep
the Portland area by about midnight. High
today will, once again, struggle to climb into the
mid 30s. Temperatures will rapidly chill back into
as soon as the sun sets or if precipitation begins.
The precipitation will begin mostly as snow or sleet
south valley, with a likely transition to sleet and
rain, as the air aloft continues to warm. Light
surface winds will continue to supply low-level cold
throughout the valley. However, there may be enough
warming, in the south valley, to change
just plain rain as early as Saturday morning.
north, precipitation will be more likely to begin as
due to the deeper layer of cold air, especially in
Portland area and in the Columbia Gorge. A
sleet and/or freezing rain is possible in the north
during the day Saturday, with portions of the
possibly changing to plain rain.
Forecast precipitation amounts vary from around
an inch (water equivalent) to around four-tenths of
inch. However, even small amounts of snow, sleet,
freezing rain can make for very hazardous travel
so be prepared for wintry travel conditions in the
Willamette Valley tonight and Saturday. It is
the bands of precipitation will stall over the north
Saturday, which could end up producing more
amounts of snow and ice there.
NNE 0-6 this morning, NNE 3-6 this afternoon.
NNE 5 this morning, NNE 5 this afternoon.
Atmospheric Ventilation Conditions:
Maximum mixing height today will be near 1500 feet.
Ventilation index 8.
Salem's high temperature today will be near 34.
Minimum relative humidity will be near 51%.
Salem sunset tonight: 4:31pm; sunrise tomorrow:
Precipitation is expected to taper off Sunday, with
low-level flow turning onshore across most of the
That should help most of the Willamette Valley
just plain rain. However, there could still be
air coming out of the Columbia Gorge to keep wintry
precipitation in the immediate Portland area.
weather system is forecast to come onshore late
There could still be enough cold air remaining in
Columbia Gorge, and the immediate Portland area, for
wintry mix of precipitation, but the rest of the
Valley should get just rain. Even the Gorge should
scoured out by Tuesday, with warmer Pacific air
into the region.
Tomorrow (12 Dec): Snow, Sleet, or Freezing Rain...Likely
Changing to Rain South. 28/35
Sun (13 Dec): Showers...Possible Wintry Mix Near the
Gorge. Snow above 1500 feet. 32/42
Mon (14 Dec): Mostly Cloudy. Chance of Rain...Possible
Wintry Mix North. 32/40
Tue (15 Dec): Rain. Possibly Starting as Freezing Rain
Wed (16 Dec): Mostly Cloudy and Warmer. Rain Likely
Thu (17 Dec): Rain Turning to Showers. 42/49
Fri (18 Dec): Mostly Cloudy. Chance of Rain. 38/48
weather at oda.state.or.us
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