[willamette-fcst] Forecast - Tuesday, December 8th, 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: 
     Tuesday, December 8th, 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 weak upper-level disturbance, in the cold northerly flow
     aloft, will drop southward, from British Columbia to just
     off the Oregon Coast this afternoon.  It does not appear as
     if it will have enough moisture to bring any precipitation
     to the region, so skies should stay mostly sunny over western
     Oregon.  There will be some middle and high clouds, mainly near
     the coast.  Offshore pressure gradients should relax slightly
     today, with some decrease in the north-northeasterly winds
     across western Oregon.

     After a very cold start, with western Oregon temperatures
     mostly in the teens, afternoon highs will struggle to around
     the freezing mark in the Willamette Valley.  I\'ll have a rundown
     of the cold morning minimums on the noon update.

Surface Winds:
     NNE 5-15 this morning, NNE 5-15 this afternoon.
Transport Winds:
     NNE 10 this morning, NNE 10 this afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height today will be near 2700 feet.  Ventilation index 27.
High Temperature:
     Salem\'s high temperature today will be near 29.
Humidities:
     Minimum relative humidity will be near 30%.
Sunrise/Sunset:
     Salem sunset tonight: 4:31pm; sunrise tomorrow: 7:39am.

Extended Outlook:
     Cold and dry northerly flow aloft will continue Wednesday
     and Thursday.  Decreasing surface winds will allow for even
     colder overnight temperatures across western Oregon.  Mostly
     sunny skies will help afternoon highs recover to around freezing.  

     By Friday, a westerly flow aloft will begin to undercut the
     offshore ridge...taking Pacific storm systems into
     California.  The flow aloft over Oregon will back from
     northerly to northwesterly.  Clouds will be on the increase
     across extreme southern Oregon, but skies should remain
     mostly sunny over the Willamette Valley with moderating temperatures.

     By Saturday morning, moisture is forecast to spread
     northward into the Willamette Valley. The air mass aloft
     will be warming, but continued offshore flow at the surface
     should allow enough low-level cold air to remain in place
     for precipitation to fall mainly as snow, sleet, or freezing
     rain. there may be enough warming for areas of the central
     and southern valley to changeover to plain old rain, but
     expect conditions to remain icy in the Portland area and in
     the Columbia Gorge.

     By Sunday, most of the Willamette Valley should see
     temperatures moderate to above freezing, with precipitation
     falling as rain.  However, there may still be areas of
     wintry precipitation in and near the Columbia Gorge.  A much
     warmer weather system is forecast to come onshore late
     Monday, which should scour out any remaining low-level cold
     air trapped in the Gorge.

Tomorrow (09 Dec):  Mostly Sunny and Cold.  11/30

Thu (10 Dec):  Mostly Sunny and Cold.  15/34

Fri (11 Dec):  Mostly Sunny and Cold.  19/38

Sat (12 Dec):  Snow, Sleet, or Freezing Rain Likely.  Likley Changing to Rain South.  28/35

Sun (13 Dec):  Chance of Rain...Possible Wintry Mix Near the Gorge.  32/42

Mon (14 Dec):  Rain Increasing Late.  Turning Warmer.  36/50

Tue (15 Dec):  Rain Likely.  Mild.  42/52

ODA Meteorologist
weather at oda.state.or.us