[willamette-fcst] Forecast - Thursday, September 10th, 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: 
     Thursday, September 10th, 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:
     An upper-level ridge of high pressure will begin building
     over the region today and last into the weekend. Visible
     satellite imagery showed low clouds covering much of the
     Willamette Valley this morning with areas of fog along the
     coast.  Skies were sunny over the remainder of the state. 
     The areas of morning fog and low clouds will give way to
     sunshine this aftenoon. Warming aloft will allow Willamette
     Valley highs to climb into the low to mid 80s but also keep
     mixing heights below 3000 feet today. North-northeasterly
     transport winds may allow for limited open burning, on the
     extreme west side of the valley, around midday. 

Surface Winds:
     N 5-10 this morning, N 5-15 this afternoon.
Transport Winds:
     NE 10 this morning, N 12 this afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height today will be near 2500 feet.  Ventilation index 30.
High Temperature:
     Salem\'s high temperature today will be near 86.
Humidities:
     Relative humidity drops to 50% by 2pm.
     Minimum relative humidity will be near 31%.
Sunrise/Sunset:
     Salem sunset tonight: 7:32pm; sunrise tomorrow: 6:46am.

Extended Outlook:
     With a strong upper-level ridge anchored over the region
     Friday and Saturday, the surface thermal trough will
     strengthen over western Oregon.  Downsloping northeasterly
     winds, off the Cascades, may warm valley temperatures over
     the 90-degree mark under sunny skies.

     The upper-level ridge, and associated surface thermal
     trough, are forecast to shift east of the state by late
     Saturday, with increasing southerly flow aloft.  That will
     introduce some mid and high-level moisture into the state
     and enough instability for an increasing chance of
     thundershowers...mainly south and over the Cascades. 
     Increasing onshore flow will initiate a cooling trend
     Sunday, with temperatures dropping back to near-normal.

     The flow aloft is forecast to become more westerly by
     Monday, which would push the thunderstrom threat well east
     of the region but maintain a cooling onshore flow.  There
     may be a little warming Tuesday, ahead of a cold front
     forecast to come onshore Wednesday.

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

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

Sun (13 Sep):  Partly Cloudy.  Chance of T-Storms...Mainly South & near the Cascades.  55/77

Mon (14 Sep):  Partly Sunny.  54/73

Tue (15 Sep):  Mostly Sunny.  53/77

Wed (16 Sep):  Mostly Cloudy.  Increasing Chance of Light Rain...Mainly North.  53/74

Thu (17 Sep):  AM Clouds...Partly Sunny.  52/75

ODA Meteorologist
weather at oda.state.or.us