[willamette-fcst] Forecast - Monday, February 9th, 2009

Mon Feb 9 11:57:52 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.

NOON UPDATE

Issued: 
     Monday, February 9th, 2009 at 12:00pm.

Burn Advisory:
     Agricultural burning is allowed.  Suggested burn times are from now until 3:30pm.
     Straw stack burning is allowed from now until 3:30pm.

Weather Discussion:
     A Pacific cold front dropped between one and two-tenths of
     an inch of rain along the coast Sunday with lighter amounts
     inland.  Snow levels dropped to about 2000 feet Sunday
     afternoon, with about 1-3 inches of new snow falling in the
     Cascades.  After a mostly sunny afternoon Saturday, with
     Willamette Valley temperatures in the low to mid 50s, cloudy
     skies held highs in the mid to upper 40s Sunday afternoon.

     The cold front pushed east of the Cascades Sunday night with
     clearing skies and a cool air mass allowing temperatures to
     drop below freezing across most of western
     Oregon...including along the coast.  Hillsboro and Eugene
     were a couple of the colder spots, in the Willamette Valley,
     both recording minimums of 26 degrees.  McMinnville and
     Aurora dipped to 27.  Corvallis and Salem bottomed out at 30
     and 31 degrees respectively.  Along the coast, Astoria had a
     low of 29 degrees with tempertures locally dropping below
     freezing south to Brookings.  Meanwhile, cloudy skies and
     areas of very light snow kept central and eastern Oregon
     temperatures mostly in the 20s overnight, with a few areas
     dropping in the teens.

     An impressive line of showers, associated with an
     upper-level trough, moved onshore at mid-morning. The air
     mass with these showers was cold enough to bring snow
     showers to sections of the coastal strip.  About one-half
     inch of snow fell in Lincoln City with snow showers also
     reported in Astoria. The upper-level trough had pushed
     slightly east by late this morning and was bringing snow
     showers to the coastal range.  Some rain and snow showers
     were also making their way into the western half of the
     Willamette Valley.  McMinnville was reporting a light snow
     shower at 11am, with a temperature of just 33 degrees. 
     Salem and Eugene had warmed into the low 40s, just ahead of
     the upper-level trough.  The air aloft is very cold, so the
     showers should cool valley temperatures back down into the
     mid 30s early this afternoon.  

     The snow level will be between 500 and 1000 feet, but wet
     snow could mix to the valley floor at times.  Total
     precipitation values will generally be less than one-tenth
     of an inch.  High temperatures will only climb into the low
     to mid 40s.  A transitory ridge of high pressure will bring
     some partial clearing overnight with temperatures, once
     again, dropping to near or below the freezing mark across
     most of western Oregon.

     The Salem sounding from early this morning showed a very
     cold air mass aloft.  The freezing level was measured at
     just 2100 feet, which will likely drop further with the
     passage of the upper-level trough early this afternoon.  The
     cold air aloft will combine with daytime heating to produce
     significant mixing of the atmosphere, making for good
     ventilation conditions across western Oregon this afternoon.
     Southerly low-level winds should veer to westerly, in the
     wake of the trough later this afternoon.  Partial clearing
     overnight will combine with the cold air mass to drop valley
     temperatures to near or below freezing.

Surface Winds:
     WSW 5-12 this afternoon.
Transport Winds:
     W 12 this afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height today will be near 3000 feet.  Ventilation index 36.
High Temperature:
     Salem\'s high temperature today will be near 43.
Humidities:
     Minimum relative humidity will be near 62%.
Sunrise/Sunset:
     Salem sunset tonight: 5:32pm; sunrise tomorrow: 7:20am.

Extended Outlook:
     Another cold Pacific storm is forecast to spread clouds and
     precipitation back onshore Tuesday morning.  The air mass
     will remain quite cold during this entire storm. 
     Precipitation may begin as snow, all the way to sea level,
     with the snow level lifting to no higher than about 2000
     feet in the afternoon (lower in the north valley).  As the
     low-pressure center is drops southward, along the Oregon
     Coast, late Tuesday, cool outflow from the Columbia Gorge will
     maintain very low snow levels, especially in the north valley.

     The National Weather Service has issues a Winter Storm
     Watch, for 3-6 inches of possible snow Tuesday, in the
     coastal range, the Columbia Gorge, and the western Cascade
     foothills (above 1000 feet).  The Cascades will also likely
     see up to 6 inches of new snow. Wet snow could fall on the
     valley floors, but significant accumulations are not
     expected below 500 feet.  This system will need to be
     watched closely, because it has the potential to produce
     sticking snow even at sea level, especially in the extreme
     northern Willamette Valley.

     The rain and snow should taper off by early Wednesday, as
     the low-pressure center moves inland into northern
     California.  A few showers or flurries are still possible
     into Wednesday...especially in the south valley.  The snow
     level should be around 500-1000 feet.  Wednesday morning
     temperatures will be near freezing with afternoon highs
     warming into the mid 40s.  The next system is forecast to
     take more of a southerly track, moving mainly into northern
     California.  Snow levels will remain very low with some rain
     and snow possibly spreading as far as the oregon/Washington
     border late Thursday and Friday.

     Computer models are fairly consistent in forecasting a
     split-flow jet stream pattern Saturday through Monday, with
     weather systems moving by both north and south of Oregon. 
     It is too far out to tell if the region will stay completely
     dry during that time period, but it is possible. Temperatures
     will slowly moderate but should remain below normal.

Tomorrow (10 Feb):  Rain/Snow Mix.  Significant Snow Above 1000 Feet.  31/42

Wed (11 Feb):  Decreasing areas of light Rain/Snow.  Partial PM Clearing.  32/46

Thu (12 Feb):  Increasing Clouds.  Chance of Rain/Snow Mix.  32/45

Fri (13 Feb):  Mostly Cloudy.  Chance of Rain/Snow Mix.  32/45

Sat (14 Feb):  Gradual Clearing and Cool.  30/47

Sun (15 Feb):  Partly Cloudy and Cool.  28/48

Mon (16 Feb):  Partly Cloudy and Cool.  30/50

ODA Meteorologist
weather at oda.state.or.us