[willamette-fcst] Forecast - Friday, December 4th, 2009

[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: 
     Friday, December 4th, 2009 at 9:00am.

Burn Advisory:
     Agricultural burning is allowed.  Suggested burn times are from 12:00pm until 2:30pm.
     Stack burning is not allowed.

Weather Discussion:
     A dry and cool northwesterly flow aloft is directing a an
     upper-level disturbance southward across southern British
     Columbia this morning.  Satellite imagery shows very limited
     moisture with this system, but it was pushing some low
     clouds onto the northern Oregon Coast.  The remainder of
     Oregon had mostly sunny skies this morning, with the
     expection of areas of icy valley fog.  Enough cold and dry
     low-level air has filtered into the Willamette Valley to
     inhibit fog formation, except for in the extreme south valley. 

     It was cold again this morning, with mid-morning
     temperatures in the 20s and low 30s across western Oregon. 
     The ODA surface analysis showed weak pressure gradients
     across the region and winds were generally light.  A cool
     weather system is forecast to drop southward, across
     Washington and northern Oregon, later today and tonight.  It
     will have very limited moisture but will bring a chance of
     spotty light rain and snow to the region.  Snow levels will
     rapidly drop to around 1000 feet, or lower, Saturday.

Surface Winds:
     Var 0-6 this morning, NNW 5-10 this afternoon.
Transport Winds:
     Var 3 this morning, NW 7 this afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height today will be near 1700 feet.  Ventilation index 12.
High Temperature:
     Salem\'s high temperature today will be near 45.
Humidities:
     Minimum relative humidity will be near 50%.
Sunrise/Sunset:
     Salem sunset tonight: 4:31pm; sunrise tomorrow: 7:35am.

Extended Outlook:
     An Arctic cold front will be driven southward, across
     Washington and Oregon, Saturday night and Sunday, by a
     strong northerly flow aloft.  This front will not have a lot
     of moisture to work with but may produce some flurries or a
     dusting of snow across the lowlands of western
     Oregon...including the coastline.  Quite cold and dry
     conditions will follow the Arctic cold frontal passage later
     Sunday and Monday.  Weak impulses, in the cold northerly
     flow, may bring some flurries to western Oregon Tuesday and
     Wednesday, along with reinforcing surges of cold air.

     Cold easterly winds will increase, in and near the Columbia
     River Gorge, beginning this weekend, making for very low
     windchill values.  Morning minimums will drop into the teens
     and 20s across the Willamette Valley, Monday and Tuesday,
     with highs likely staying at or below freezing, even with
     some sunshine.

     A westerly flow aloft is forecast to undercut the offshore
     ridge and begin introducing moisture into California by next
     Wednesday.  Some moisture may extend northward, into Oregon,
     by Thursday, but that is questionable.  It now appears as if
     the mostly dry northerly flow will dominate through most of
     next week...decreasing the threat of significant snow but
     keeping temperatures frigid. Some moderation in temperatures
     will likely begin by Friday, but no significant moisture is
     forecast to be directed into the region.

Tomorrow (05 Dec):  Partly Cloudy.  Increasing Clouds with Snow Flurries Late.  28/44

Sun (06 Dec):  Chance of Light Snow Early.  Turning Partly Cloudy and Cold.  27/31

Mon (07 Dec):  Partly Cloudy and Much Colder.  Chance of Flurries.  19/30

Tue (08 Dec):  Partly Cloudy and Cold.  Chance of Flurries.  17/31

Wed (09 Dec):  Partly Cloudy and Cold.  Chance of Flurries.  17/31

Thu (10 Dec):  Partly Cloudy and Cold.  Chance of Flurries.  18/32

Fri (11 Dec):  Partly Cloudy and Cold.  Chance of Flurries.  22/35

ODA Meteorologist
weather at oda.state.or.us