[willamette-fcst] Forecast - Tuesday, February 16th, 2010

[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, February 16th, 2010 at 9:00am.

Burn Advisory:
     Recommended burn times for agricultural burning are from now to 3:30pm.
     Stack burning is not allowed.

Weather Discussion:
     A weak cold front spread rain across western Oregon
     overnight and was pushing east of the Cascades this morning.
     Satellite imagery and surface reports showed some breaks
     in the clouds across western Oregon.  Doppler radar showed
     a few showers over mainly the extreme south valley, with
     the bulk of the activity now east of the Willamette Valley.
 
     Much of the Willamette VaLley picked up about one-quarter of
     an inch of rain overnight, with up to three-quaters of an
     inch falling along the north coast.  Areas of light rain
     were falling across central and eastern Oregon this morning,
     but amounts were generally well less than one-tenth of an inch.

     This was a mild weather system, with the freezing levels
     over Salem and Medford measured at 7100 and 7800 feet
     respectively early this morning.  ODOT road cameras showed
     wet pavement over the Cascade passes with pass temperatures
     in the mid 30s this morning.  Even in the wake of the cold
     front, mild westerly winds were keeping temperatures in the
     low 50s across the Willamette Valley.

     High pressure will rapidly build over the region today, with
     showers ending and skies slowly clearing.  That air aloft is
     warm enough to support western Oregon temperatures climbing
     into the mid to upper 50s this afternoon.  Transport winds
     will likely become northerly this afternoon, which is not a
     good direction for stack burning, so it was not allowed
     today.  Clearing skies and light north winds will allow
     temperatures to drop into the mid to upper 30s across the
     Willamette Valley tonight with areas of fog forming.

Surface Winds:
     WSW 3-8 this morning, N 3-8 this afternoon.
Transport Winds:
     WSW 6 this morning, N 5 this afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height today will be near 2000 feet.  Ventilation index 12.
High Temperature:
     Salem\'s high temperature today will be near 59.
Humidities:
     Minimum relative humidity will be near 55%.
Sunrise/Sunset:
     Salem sunset tonight: 5:42pm; sunrise tomorrow: 7:10am.

Extended Outlook:
     An upper-level ridge of high pressure is forecast to amplify
     just off the west coast Wednesday and Thursday, with a dry
     northerly flow aloft over Oregon.  Increasing offshore flow
     at the surface will help to clear skies, after areas of
     morning fog, which will mainly form in in the central and
     southern valley.  Increasing easterly outflow, from the
     Columbia Gorge, will likely keep fog out of the extreme
     north valley.

     Drier air will make for greater temperature spread between
     overnight minimums and daytime maximums.  Valley highs will
     vary, depending on the local duration of fog and low clouds.
     The air mass puring into the Columbia Basin, from Canada,
     will likely be cool enough to keep temperatures from climbing
     much above 60 in the Willamette Valley, but downsloping winds
     could send coastal temperatures into the mid 60s.

     Some moisture may undercut the upper-level ridge and begin
     moving into southern Oregon late in the week.  It is
     possible that some of this moisture could advance northward
     into the Willamette Valley by the weekend.  The chance of
     rain increases next week.

Tomorrow (17 Feb):  Areas of AM Fog...Mainly Central and South.  Partly Cloudy.  34/58

Thu (18 Feb):  Patchy AM Fog...Mainly South.  Mostly Sunny and Mild.  34/62

Fri (19 Feb):  Partly Cloudy and Mild with Continued Offshore Flow.  35/60

Sat (20 Feb):  Partly Cloudy.  34/58

Sun (21 Feb):  Mostly Cloudy.  Slight Chance of Rain.  36/55

Mon (22 Feb):  Chance of Rain.  38/54

Tue (23 Feb):  Chance of Rain.  40/54

ODA Meteorologist
weather at oda.state.or.us