[willamette-fcst] Forecast - Wednesday, May 7th, 2008

Wed May 7 15:40:25 PDT 2008

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, May 7, 2008 at 4:45 pm.

Burn Advisory For Thursday, May 8, 2008:
     Agricultural burning is allowed.  Suggested burn times are from 8:00am until 6:30pm.
     Straw stack burning is allowed from 8:00am until 6:30pm.

Weather Discussion:
     A thick marine layer surged into the Willamette Valley last
     night in response to a dry but fairly cool upper-level
     trough that moved across the region.  The air mass cooled
     considerably with the freezing level over Salem dropping
     from 9000 feet Morning to just 4200 feet this morning.  Low
     clouds were extensive today across Western Oregon with areas
     of drizzle.  Only the extreme southern coast and
     Southwestern Oregon saw sunshine.

     The late-afternoon visible satellite picture showed some
     breaks in the low clouds beginning to appear...mainly over the
     coastal range.  Temperatures were 5-10 degrees cooler today in
     the valley with afternoon readings struggling to reach the mid
     50s under cloudy skies.

     High clouds from another weak disturbance, in the
     northwesterly flow aloft, were showing up nicely on infrared
     satellite imagery this afternoon, as they moved over NW
     Oregon.  That will help maintain the strong onshore flow
     across the state overnight.  Skies were mostly sunny east of
     the cascades today, but cool west winds at 15-30 mph kept
     temperatures in the 50s and 60s.  Ontario, near the Idaho
     border, was the warm spot in the state this afternoon at 71
     degrees.

     The marine low clouds will break up this evening across
     Western Oregon...only to thicken up again by Thursday
     morning with areas of drizzle.  Temperatures may locally
     fall into the upper 30s overnight, but low 40s will be
     common.  East of the Cascades, fair skies will combine with
     a cool air mass to allow temperatures to locally drop below
     the freezing mark in wind-sheltered valleys.

     Another dry but cool upper-level trough is foreast to move
     onshore Thursday and across Oregon Thursday night.  That
     will likely keep generally cloudy skies over Western Oregon
     with strong onshore flow at the surface holding temperatures
     mostly in the 50s.  The trough may be strong enough to
     produce a few sprinkles around the state...mainly over the
     mountains.  The snow level will remain near 4000 feet but
     little in the way of precipitation is expected.

Surface Winds:
     WNW 5-8 Thursday morning, NW 8-15 Thursday afternoon.
Transport Winds:
     NW 8 Thursday morning, NW 10-15 Thursday afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height Thursday will be near 5000 feet.  Ventilation index 40.
High Temperature:
     Salem\'s high temperature Thursday will be near 58.
Humidities:
     Minimum relative humidity will be near 45%.
Sunrise/Sunset:
     Salem sunset tonight: 8:26pm; sunrise Thursday: 5:51am.

Extended Outlook:
     After a cool start to the day Friday, a weak ridge of high
     pressure should bring partly sunny and warmer weather Friday
     afternoon with temperatures recovering to near normal across
     the Willamette Valley.  A weak cold front is forecast to
     approach the coastline Saturday with a chance of light rain
     moving onshore by late afternoon.  Temperatures will likely
     climb above normal, ahead of the front, Saturday and then
     drop back below normal with a chance of showers Sunday.  

     Showers are forecast to taper off Monday, as the upper-level
     trough pushes east of the region.  A warm front is forecast
     to bring clouds and perhaps light rain as far south as
     Northwestern Oregon Tuesday, but that may be the last threat
     of rain for awhile...

     The long-range computer models are still indicating the
     possibility of much warmer and dry weather for the latter
     half of next week...extending into the following weekend. 
     We could be in for a taste of summer-like weather with
     strong offshore surface flow and Willamette Valley
     temperatures shooting well into the 80s by next Friday.

Thu (08 May):  Chance of AM Drizzle.  Slight Chance Showers. Snow Level 4000 Feet.  40/58

Fri (09 May):  Becoming Partly Cloudy.  37/64

Sat (10 May):  Increasing Clouds.  Chance of Light Rain Late...Mainly North.  40/69

Sun (11 May):  Chance of Showers and Cooler.  Snow Level Dropping to 3-4000 Feet.  43/58

Mon (12 May):  Mostly Cloudy.  Chance of a Shower Early...Afternoon Clearing.  40/63

Tue (13 May):  Chance of Light Rain North.  Partly Cloudy South.  45/65

Wed (14 May):  Becoming Mostly Sunny and Warmer.  46/72

Thu (15 May):  Sunny and Very Warm.  49/80

ODA Meteorologist
weather at oda.state.or.us