[willamette-fcst] Forecast - Wednesday, October 15th, 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.

...There will be no noon update today.  The next update will be issued at 9:00am tomorrow...

Issued: 
     Wednesday, October 15th, 2008 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 building ridge of high pressure cleared skies Tuesday
     evening and allowed Willamette Valley temperatures to drop to
     near the freezing mark this morning, with areas of dense fog
     forming. Hillsboro, McMinnville, and Corvallis all dropped
     to 30 degrees.  Dense fog helped Eugene stay above freezing
     at 33.  Salem dipped to 34 and Aurora 35.

     Warming aloft and cool surface temperatures will maintain a
     low-level temperature inversion over the valley today, so
     mixing heights should remain at or below 2000 feet. The ODA
     surface analysis showed high pressure over Western Oregon
     with little weak pressure gradients over the Willamette
     Valley.  Transport winds will be light and variable, making
     for poor ventilation conditions.

     Satellite imagery showed high clouds already beginning to spread
     over Western Oregon, in response to a weak warm front well
     offshore.  Valley fog will be slow to give way to increasing
     high clouds today, so high temperatures will struggle into the
     mid to upper 50s (about 5-10 degrees below normal).

     The warm front could spread some light rain onto
     the north coast by late this afternoon with a little rain
     possible in the Northern Willamette Valley tonight and
     Thursday.  More clouds will keep temperatures warmer
     tonight with minimums generally in the low 40s.

Surface Winds:
     Var 0-4 this morning, Var 4 this afternoon.
Transport Winds:
     NE 5 this morning, Var 4 this afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height today will be near 2000 feet.  Ventilation index 10.
High Temperature:
     Salem\'s high temperature today will be near 57.
Humidities:
     Minimum relative humidity will be near 50%.
Sunrise/Sunset:
     Salem sunset tonight: 6:26pm; sunrise tomorrow: 7:30am.

Extended Outlook:
     A warm front will bring cloudy skies to the region Thursday
     with a chance of sprinkles or very light rain in the north
     valley.  Increasing southeasterly winds will help stir the
     air, break up the fog, and warm temperatures into the low to
     mid 60s.

     The warm front is forecast to push north of the region
     Friday with southerly winds warming temperatures into the
     mid to upper 60s.  A cold front is forecast to bring a
     chance of light rain by Friday night...mainly to the north
     valley.  Ahead of the cold front, there may be a burning
     opportunity, Friday afternoon, for remaining fields.

     A weak upper-level trough will maintain onshore flow
     Saturday with a transitory upper-level ridge building over
     the west coast Sunday.  Increasing southwesterly flow aloft
     will send a stronger cold front onshore Monday.  A
     transitory ridge is forecast for Tuesday with a weak weather
     system slated for late Wednesday and Thursday.

Tomorrow (16 Oct):  Cloudy.  Chance of Sprinkles/Light Rain...Mainly North.  41/64

Fri (17 Oct):  Increasing Clouds.  Chance of Light Rain Late.  47/67

Sat (18 Oct):  Slight Chance of a Showers Early...Becoming Partly Sunny.  46/65

Sun (19 Oct):  Increasing High Clouds and Mild.  45/67

Mon (20 Oct):  Rain Developing.  Snow Level Dropping to near 4000 Feet Late.  47/59

Tue (21 Oct):  Chance of Showers Early...Partly Sunny Afternoon.  45/61

Wed (22 Oct):  Increasing Clouds...Chance of Rain Late.  42/64

ODA Meteorologist
weather at oda.state.or.us