[willamette-fcst] Forecast - Tuesday, February 10th, 2009
Willamette Valley Ag/Burning Forecast
willamette-fcst at listsmart.osl.state.or.us
Tue Feb 10 12:16:36 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.
Tuesday, February 10th, 2009 at 12:00pm.
Agricultural burning is allowed. Suggested burn times are from now until 3:30pm.
Straw stack burning is allowed from now until 3:30pm.
Another in a series of cold weather systems brought light snow to most
of western Washington and the interior of western Oregon this morning,
north of about Roseburg. There was little accumulation below 500 feet
with an inch or two of snow at elevations above about 1000 feet. The
first band of precipitation moved east of the Cascades around mid-morning,
with the snow tapering off and mixing with rain across the Willamette
Valley. Rain was beginning to increase again, along with the south wind,
by late this morning.
Satellite imagery showed the main cold front nearing the coastline late
this morning, with Doppler radar showing a more substantial surge of
moisture moving onshore. The ODA surface analysis showed rapidly increasing
southeasterly pressure gradients across western Oregon, in response to the
approaching cold front. South-southeasterly winds had increased to between
10 and 15 mph in the Willamette Valley, with gusts to near 25 mph in the Salem
area. Southerly winds were also rapidly increasing along the coast, with
Lincoln City getting gusts to more than 40 mph. Southerly winds were helping
to warm temperaures into the mid and upper 30s across western Oregon.
The air mass aloft is still very cold. The freezing level over Salem early
this morning was measured at just 900 feet, and that is forecast to only rise
to about 2500 feet by late this afternoon. That puts the snow level at or
below about 1500 feet for the duration of this storm system, and the bulk of
the precipitation is yet to come. That means the mountains are going to get
a fair amount of new snow later today.
Satellite imagery showed a fairly intense low-pressure center a litle more
than 300 miles west of the central Washington Coast and continuing to drift
southeastward. It is forecast to be just off the central Oregon coast by
Wednesday morning. Cool outflow from the Columbia Gorge will increase
this afternoon, as the low-pressure center moves close to the northern
Oregon Coast. That will maintain very low snow levels in and near the
Columbia Gorge...perhaps down to river level. However, increasing southerly
winds should help snow levels stay above the valley floor, south of the
Portland area, as the main surge of moisture rolls onshore this afternoon.
Precipitation will remain as snow at elevations above about
1500 feet with 3-6 inches of snow likely this afternoon and
evening. The steady rain and snow will turn showery, in the
wake of the front, tonight, with snow levels dropping very
near the valley floors. The National Weather Service has
issued a Winter Storm Warning for the western Columbia
Gorge, where wet snow may accumulate down the river level
later today. Winter Weather Advisories are still in effect
for the coastal range, the Portland/Vancouver area, the
western Cascade foothills (above 1500 feet), and the Cascades.
Temperatures are marginal for sticking snow in the lower
elevations around Portland, because outflow from the
Columbia Gorge is not that cold. It will likely barely get
cold enough in the Gorge for snow to accumulate down to the
Columbia River level. only a couple of degrees can make the
difference between wet pavement and several inches of wet
snow, so check road conditions before planning trevel in
these areas later today and tonight. At the very least,
expect winter driving conditions today over all western
Oregon and western Washington mountain passes...including
the coastal range passes.
Temperatures in the valley should warm into the low 40s this
afternoon, as southerly winds increase and become rather
blustery (gusts to near 30 mph are possible). Southerly
winds will continue to increase along the northern and
central Oregon Coast this afternoon, where High Wind
Warnings have been issued, until 4pm, for gusts to near 65
mph. Very cold air aloft will yield reasonably high mixing
heights this afternoon. That, combined with brisk southerly
transport winds, will make for good ventilation conditions
this afternoon across the region.
The latest weather advisories from the National Weather
Service are at:
The latest road conditions across Oregon may be found at:
S 12-25 G30 this afternoon.
S 25 this afternoon.
Atmospheric Ventilation Conditions:
Maximum mixing height today will be near 3000 feet. Ventilation index 75.
Salem\'s high temperature today will be near 41.
Minimum relative humidity will be near 73%.
Salem sunset tonight: 5:34pm; sunrise tomorrow: 7:18am.
The rain and snow should taper off Wednesday, from north to
south across western Oregon, as the low-pressure center
moves inland near the southern Oregon/northern California
border. The snow level should hover around 500-1000 feet.
Wednesday morning temperatures will be near freezing with
cool northerly winds only allowing afternoon highs to warm
into the low to mid 40s. Some clearing is likely Wednesday
night and early Thursday. That will allow temperatures to
fall below the freezing mark Thursday morning. The next system
is forecast to take a slightly more of a southerly track, but
it should bring more rain and snow to western Oregon Thursday
afternoon through early Friday. The snow level should be near
the valley floors again with significant snow accumulations
possible above about 1000 feet, especially south.
Computer models are fairly consistent in forecasting a
split-flow jet stream pattern Saturday and Sunday, with
weather systems moving by both north and south of Oregon.
It is unlikely that the region will stay completely dry
during that time period, so I have kept a chane of showers
in the forecast with continued very low snow levels. A more
organized system may move onshore Monday night and Tuesday,
but that is getting too far out to call at this point.
Temperatures will stay well below normal through the weekend
and possible warm to near normal by next Tuesday.
Tomorrow (11 Feb): Decreasing Areas of light Rain/Snow. Partial PM Clearing. 32/46
Thu (12 Feb): Increasing Clouds. Chance of PM Rain/Snow Mix. 28/45
Fri (13 Feb): Decreasing Rain and Snow. Snow Level Near 1000 Feet. 32/45
Sat (14 Feb): Partial Clearing and Cool. 28/47
Sun (15 Feb): Chance of Showers and Cool. Snow Level Near 2000 Feet. 28/48
Mon (16 Feb): Increasing Clouds. Chance of Rain Late. Snow Level 3000 feet. 32/48
Tue (17 Feb): Increasing Rain and Warmer. Snow Level 4000 Feet. 36/50
weather at oda.state.or.us
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