[willamette-fcst] Forecast - Wednesday, August 19th, 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.

...State Fire Marshal Conditions are likely later this afternoon...

Issued: 
     Wednesday, August 19th, 2009 at 9:00am.

Burn Advisory:
     Agricultural burning is not recommended.
     Preparatory burning is not allowed.
     Propane flaming is not allowed.
     Stack burning is not allowed.

Weather Discussion:
     A strong ridge of high pressure will move directly over
     Washington and Oregon today, with Willamette Valley highs
     near 100 degrees. Northeasterly transport winds may allow
     for open burning of fields, on the extreme western side of
     the south valley, late this morning. Other open burning is
     highly unlikely today.

     The Salem sounding showed further warming aloft this
     morning, so valley highs should climb to around 100 degrees
     this afternoon, after hitting the mid 90s Tuesday (most
     locations were only a degree or two shy of daily record
     highs).  Astoria tied their record high Tuesday with 82 degrees.  

     The mid-morning ODA surface analysis showed the thermal
     trough covering all of western Oregon and extending into
     south-central Washington.  Visible satellite imagery showed
     considerable low clouds just off the length of the
     Washington and Oregon coastline this morning...an indication
     of increasing westerly low-level flow approaching the coast.
      Skies remained mostly clear over Oregon.  Mid-morning
     temperatures were in the 50s along the coast but had already
     warmed into the low 70s in portions of the Willamette Valley
     (a few degrees warmer than 24 hours ago in some locations).

     Onshore flow will cool the immediate coastline into the 60s
     and low 70s today, while the interior valleys of western
     Oregon continue to heat up.  Many daily records are in
     jeopardy, including the record high of 98 degrees for Salem
     (previously set in 1939) and 94 for Portland (previously set
     in 1967).  The record high of 100 for Eugene (also set in
     1939) may stand.  It will be close, because temperatures
     aloft support surface temperatures reaching the century mark
     this afternoon. Like yesterday, the combination of high
     temperatures and low humidities will likely put much of the
     valley into State Fire Marshal Conditions during the
     mid-to-late afternoon period.

Surface Winds:
     Var 0-6 this morning, NW 5-10 this afternoon.
Transport Winds:
     NE 8 this morning, SE 4 this afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height today will be near 3200 feet.  Ventilation index 26.
High Temperature:
     Salem\'s high temperature today will be near 100.
Humidities:
     Minimum relative humidity will be near 21%.
Sunrise/Sunset:
     Salem sunset tonight: 8:11pm; sunrise tomorrow: 6:20am.

Extended Outlook:
     The upper-level ridge is forecast to move over Idaho
     Thursday, with increasing southwesterly flow aloft over
     western Oregon.  Onshore flow will likely develop Thursday
     afternoon...cooling temperatures about 10 degrees and likely
     creating a burning opportunity.  A fairly strong marine push
     is forecast for Thursday night with low clouds likely
     forming over the western valleys by Friday morning. Increasing
     southwesterly flow aloft, and onshore flow at the surface,
     will continue the cooling trend across western Oregon on Friday.

     A weak trough is forecast to bring a deeper layer of marine
     air into the Willamette Valley by Saturday.  Onshore flow is
     forecast to continue Sunday through Tuesday with little to
     no rainfall and seasonal temperatures.

Tomorrow (20 Aug):  Mostly Sunny and not as Hot.  64/90

Fri (21 Aug):  Mostly Sunny and Cooler.  56/85

Sat (22 Aug):  AM Clouds.  PM Sunshine.  53/81

Sun (23 Aug):  AM Clouds.  PM Sunshine.   54/84

Mon (24 Aug):  Partly Cloudy.   54/86

Tue (25 Aug):  Partly Cloudy.   54/82

Wed (26 Aug):  Partly Cloudy.  54/81

ODA Meteorologist
weather at oda.state.or.us