[willamette-fcst] Forecast - Tuesday, December 16th, 2008

[Willamette Valley Ag/Burning Forecast]

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: 
     Tuesday, December 16th, 2008 at 9:00am.

Burn Advisory:
     Agricultural burning is not recommended.
     Stack burning is not allowed.

Weather Discussion:
     Cold and dry Arctic air will bring a mostly sunny day to
     Oregon today with ofshore flow across western Oregon. 
     Morning minimums were the coldest of the year with Corvallis
     dipping to 9 degrees and teens common across the Willamette
     Valley.  Highs today should stay below freezing with lighter
     northerly winds.

Surface Winds:
     N 5-10 this morning, N 5-10 this afternoon.
Transport Winds:
     NNE 10 this morning, NNE 12 this afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height today will be near 1600 feet.  Ventilation index 19.
High Temperature:
     Salem\'s high temperature today will be near 29.
Humidities:
     Minimum relative humidity will be near 40%.
Sunrise/Sunset:
     Salem sunset tonight: 4:32pm; sunrise tomorrow: 7:45am.

Extended Outlook:
     The next weather system is forecast to drop down the British
     Columbia coastline, and into the Pacific Northwest,
     Wednesday.  The air mass will initially be cold enough for
     the precipitation to begin as snow across western Oregon
     with some accumulation likely.  The track of the storm may
     bring low-pressure inland, across southwestern Washington,
     late Wednesday.  If that occurs, then enough onshore flow
     may develop to change the snow to rain along the Oregon
     coast, and perhaps the lowest elevations in the southern and
     central Willamette Valley, late in the day.  It appears that
     conditions will likely stay cold enough for precipitation to
     remain as snow in the Portland area, due to cold outflow
     from the Columbia Gorge, but it is possible that even the
     Portland area could make the transition to rain late in the day.

     Another cold Arctic front is forecast to drop south across
     Washington and into northern Oregon Thursday morning.  The
     Arctic cold front will advance south across western Oregon
     during the day Thurssday...changing all precipitation back
     to snow with accumulations likely.  An even colder surge of
     Arctic air will pour into the region Friday, with skies
     gradually clearing and easterly winds
     increasing...especially in the Portland area.

     Another weather system is forecast to move onshore over the
     weekend and will likely produce a wintry mix of
     precipitation across the region.  The latest comuter models
     suggest that this system will track to near the central
     Oregon coast, which would keep precipitation mainly in the
     form of snow across western Oregon.  Snow totals from that
     system could potentially be very significant., It appears
     that another reinforcing shot of Arctic air may invade the
     region early next week, for a continued cold conditions.

Wed (17 Dec):  Snow Likely...Possibly Changing to Rain...Mainly South of Portland.  15/35

Thu (18 Dec):  Rain or Snow Turning to Snow.  Accumulations Likely.  31/35

Fri (19 Dec):  Snow Ending...Becoming Partly Cloudy. Continued Cold.  18/27

Sat (20 Dec):  Mostly Sunny, Cold, and Windy.  12/25

Sun (21 Dec):  Wintry Mix Likely...Perhaps All Snow.  20/32

Mon (22 Dec):  Decreasing Snow Showers...Continued Cold.  20/27

Tue (23 Dec):  Partly Cloudy and Cold.  15/27

ODA Meteorologist
weather at oda.state.or.us