[willamette-fcst] Forecast - Wednesday, September 9th, 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.

Issued: 
     Wednesday, September 9th, 2009 at 8:50am.

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 weak cold front was about 150 miles offshore at
     mid-morning and will move inland this afternoon...mainly
     into western Washington. Satellite imgery showed clouds had
     already spread across all of Washington and most of Oregon
     this morning.  Some light rain fell this morning across
     northwestern Washington, but conditions have remained dry,
     so far, south of about Olympia.  The weakening cold front
     will keep lots of clouds over western Oregon today, with some
     sprinkles possible in the extreme north valley this afternoon. 

     Temperatures were warmer across western Oregon this morning,
     due to the increase in cloud-cover overnight.  Willamette
     Valley minimums were mostly near 50 degrees.  Under mostly
     cloudy skies, Willamette Valley high temperatures should
     climb into the mid 70s this afternoon, which would likely be
     warm enough to lift mixing heights above 3000 feet. Forecast
     west-southwesterly transport winds may provide good
     ventilation for open burning this afternoon.  Damp fields
     will require fluffing, before being burned this afternoon.

Surface Winds:
     SE 5-10 this morning, SW 5-12 this afternoon.
Transport Winds:
     SSE 7 this morning, WSW 7 this afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height today will be near 5000 feet.  Ventilation index 35.
High Temperature:
     Salem\'s high temperature today will be near 77.
Humidities:
     Relative humidity drops to 50% around 2pm.
     Minimum relative humidity will be near 47%.
Sunrise/Sunset:
     Salem sunset tonight: 7:34pm; sunrise tomorrow: 6:45am.

Extended Outlook:
     A rapidly building ridge of high pressure will bring a
     return of summer-like weather, beginning Thursday afternoon.
     A surface thermal trough should build northward, along the
     Oregon Coast, turning the low-level winds offshore.  That
     could provide an opportunity to burn western valley fields
     as soon as Thursday morning.  As the thermal trough
     strengthens over western Oregon Friday and Saturday,
     downsloping winds, off the Cascades, may warm valley
     temperatures over the 90-degree mark.

     The upper-level ridge, and associated surface thermal
     trough, are forecast to shift east of the state by Sunday,
     with increasing southerly flow aloft.  Increasing onshore
     flow will initiate a cooling trend Sunday, with temperatures
     dropping back closer to normal.  Increasing southerly flow
     aloft will introduce a chance of thunderstorms, mainly over
     the Cascades, Sunday and Monday.  A weak cold front is
     forecast to come onshore until about Wednesday of next week.

Thu (10 Sep):  AM Clouds...Sunny and Warmer in the Afternoon.  NNE Winds Developing.  53/85

Fri (11 Sep):  Sunny and Very Warm.  NE Winds.  53/92

Sat (12 Sep):  Sunny and Very Warm.  Light Winds.  55/90

Sun (13 Sep):  Mostly Sunny.  Chance of T-Storms near the Cascades.  55/84

Mon (14 Sep):  Mostly Sunny.  Slight Chance of T-Storms near the Cascades.  54/80

Tue (15 Sep):  Mostly Sunny.  53/80

Wed (16 Sep):  Mostly Cloudy.  Increasing Chance of Light Rain...Mainly North.  53/75

ODA Meteorologist
weather at oda.state.or.us