[willamette-fcst] Forecast - Thursday, February 14th, 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.

          ...Next Update 9 am Tuesday, February 19th...

Issued: 
     Thursday, February 14th, 2008 at 9:00am.

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

Weather Discussion:
     A cool upper-level trough brought scattered light showers
     and low snow levels to Washington and Oregon Wednesday.  The
     air mass slowly stabilized overnight, as the trough moved
     southeastward into Nevada and Utah.  The Pacific Northwest
     is under the influence of north-northeasterly flow aloft
     this morning, with a ridge of high pressure building into
     the region.

     Temperatures dropped into the 30s overnight across Western Oregon
     with some locations falling below the freezing mark.  Astoria, Newport,
     and Corvallis all dropped to 30 degrees early this morning, while
     McMinnville dipped to 29. Hillsboro dropped to a low of 28 degrees.
     Low clouds and patchy fog helped to keep temperatures just above freezing
     in Salem and Eugene, with a lows of 35 and 33 respectively.

     The air mass aloft was still very cold early this morning. The freezing
     level over Salem was measured at just 2400 feet at 4 am.  Satellite
     imagery showed areas of low clouds in the Willamette Valley this morning,
     as a result of the continued weak onshore flow across Western Oregon.  An
     upper-level ridge will quickly build over the region today with rapid warming
     aloft and surface pressure gradients becoming northerly.  That will dry the
     air mass and help to clear the low clouds from the western valleys for mostly
     sunny skies this afternoon.  Temperatures will climb to near normal and
     freezing levels will quickly rebound to above 6000 feet by late this afternoon.

     Rapid warming aloft will reduce mixing heights this afternoon.  Combined with
     northerly winds, that will make for poor ventilation conditions over the
     Willamette Valley, so stack burning is not allowed and agricultural burning is
     not recommended. With the air mass drying out, clear skies and light winds
     tonight will allow temperatures to drop to near or below freezing across much 
     of Western Oregon with strong low-level temperature inversions developing.

Surface Winds:
     NW 5 this morning, N 5-10 this afternoon.
Transport Winds:
     NE 10 this morning, NE 10 this afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height today will be near 2000 feet.  Ventilation index 20.
High Temperature:
     Salem\'s high temperature today will be near 50.
Humidities:
     Minimum relative humidity will be near 58%.
Sunrise/Sunset:
     Salem sunset tonight: 5:38pm; sunrise tomorrow: 7:13am.

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

     Low clouds and weak onshore flow will keep temperatures from
     falling as rapidly Friday night across Western Oregon, with
     most areas staying above freezing.  A massive ridge of high
     pressure is still 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.  Surface gradients will turn offshore
     Saturday afternoon through Sunday and freezing levels will
     be near 9000 feet.  That should help afternoon temperatures
     climb to well above normal Saturday and possibly approach
     records by Sunday with valley highs in the low 60s.

     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.  There is a slight chance of rain with the first
     system Monday night.  Rain is likely by Tuesday night with a
     more seasonal stormy weather pattern forecast by the middle
     of next week.

     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 (15 Feb):  Partly Cloudy.  30/54

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

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

Mon (18 Feb):  Mostly Sunny & Continued Mild.  Chance of Light Rain Late.  36/57

Tue (19 Feb):  Chance of Rain Early...Rain Likely Late.  Snow Level Near 6000 Feet.  38/54

Wed (20 Feb):  Rain and Blustery.  Snow Level 5000 Feet.  40/50

Thu (21 Feb):  Showers and Blustery.  Mountain Snow.  Snow Level 2500 Feet.  38/48

ODA Meteorologist
weather at oda.state.or.us