[willamette-fcst] Forecast - Wednesday, February 13th, 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: 
     Wednesday, February 13, 2008 at 4:45 pm.

Burn Advisory For Thursday, February 14, 2008:
     Agricultural burning is not recommended.
     Stack burning is not allowed.

Weather Discussion:
     A cold upper-level trough brought cooler conditions and a
     few showers to Washington and Oregon today...mainly over the
     mountains.  Snow levels dropped to 1500 feet over Northern
     Oregon and 2500 feet over Southern Oregon this morning.  The
     Northern Oregon Cascades received a few new inches of snow
     overnight with flurries being reported as of late this
     afternoon.  Pass temperatures stayed in the mid to upper 20s
     this afternoon with the snow level only rising to about 2000
     feet.  The freezing level was measured over Salem this
     afternoon at just 3100 feet.

     Rainfall in the valley since Tuesday evening ranged from a
     trace in Eugene to a few hundredths of an inch...with the
     greatest amounts in the Portland area.  Up to one-quarter of
     an inch of rain fell along the Northern coast.  Doppler
     radar showed scattered light showers continuing over
     Northwest Oregon late this afternoon with valley
     temperatures generally in the mid and upper 40s. 
     Northwesterly flow aloft will turn more northerly this
     evening.  That showers should rapidly taper off, with
     clearing skies, after sunset.   Most of the valley will drop
     to near or below the freezing mark overnight with areas of
     fog forming by Thursday morning.

     After a cool and locally foggy start Thursday, an
     upper-level ridge will quickly build over the region for a
     mostly sunny and warmer afternoon.  Temperatures will climb
     to near normal and freezing levels will rebound to 5-6000
     feet by late afternoon.  Subsidence, due to the building
     ridge, will warm the air aloft and make for poor ventilation
     conditions over the valley.  Clear skies and light winds
     Thursday night will allow temperatures to drop below
     freezing across much of Western Oregon.

Surface Winds:
     Var 0-5 Thursday morning, N 5-10 Thursday afternoon.
Transport Winds:
     N 5 Thursday morning, N 10 Thursday afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height Thursday will be near 1800 feet.  Ventilation index 18.
High Temperature:
     Salem\'s high temperature Thursday will be near 50.
Humidities:
     Minimum relative humidity will be near 52%.
Sunrise/Sunset:
     Salem sunrise Thursday: 7:15 am; sunset Thursday: 5:38 pm.

Extended Outlook:
     A very weak front will ride over the top of the ridge of
     high pressure and slide across Southern British Columbia and
     Washington Friday.  Some clouds will likely make it
     southward into Oregon, with continued onshore flow, but it
     is unlikey that rain will make it this far south.  Freezing
     levels will rise to near 8000 feet by Friday afternoon, and
     valley temperatures will climb into the low to mid 50s.

     A massive ridge of high pressure is forecast to build over
     the region this weekend, which will direct storm activity
     northward into Central British Columbia and bring
     spring-like weather to Oregon and Washington.  Freezing
     levels will be near 9000 feet with increasing low-level
     offshore flow leading to near record high temperatures by Sunday.

     The strong upper-level ridge will shift eastward, over the
     Rockies, early next week.  That will allow a series of
     progressively stronger Pacific storms to move into the
     region.  Rain should return by Tuesday afternoon with an
     even stronger system forcast to bring more rain and mountain
     snow late Wednesday into Thursday.

     The February update to the Seasonal Climate Forecast is
     available on the ODA website.  You can view it by going to
     http://oregon.gov/ODA/NRD/weather.shtml#Weather_forecasts
     and clicking on:  ODA\'s Seasonal Climate Forecast in either
     PowerPoint or Adobe PDF format.  The current outlook goes
     through May, 2008.

Tomorrow (14 Feb):  Areas of Morning Fog...Becoming Mostly Sunny.  29/50

Fri (15 Feb):  Partly Cloudy.  29/54

Sat (16 Feb):  Sunny and Mild.  35/55

Sun (17 Feb):  Sunny with Near-Record Warmth.  35/60

Mon (18 Feb):  Increasing Clouds & Mild.  Chance of Light Rain Late.  36/57

Tue (19 Feb):  Rain Likely By Afternoon.  Snow Level Near 6000 Feet.  38/54

Wed (20 Feb):  Chance of Showers Early...Rain Late.  Snow Level 5000 Feet.  39/54

Thu (21 Feb):  Rain Likely & Cooler.  Snow Level 3000 Feet.  38/48

ODA Meteorologist
weather at oda.state.or.us