[willamette-fcst] Forecast - Wednesday, August 27th, 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.

Issued: 
     Wednesday, August 27th, 2008 at 9:00am.

Burn Advisory:
     Agricultural burning is allowed.  Suggested burn times are from 12:00pm until 7:00pm.
     Preparatory burning is not allowed.
     Propane flaming is not allowed.
     Straw stack burning is allowed from 12:00pm until 7:00pm.

Weather Discussion:
     A moist Pacific storm system brought a soaking rain to
     northwest Washington overnight with the northern Washington
     Coast getting over an inch of rain.  More than one-quarter
     of an inch of rain fell, from Olympia northward, across the
     interior of Western Washington.  The trailing cold front
     brought light rain to the northern Oregon Coast with areas
     of very light rain and drizzle falling early this morning in
     the northern Willamette Valley.  Almost one-quarter of an
     inch of rain fell overnight at Astoria.  The Portland
     Airport picked up .01 inches in the pre-dawn hours this
     morning with only trace amounts reported south of Portland
     to Eugene.

     The cold front was weakening and moving trough the northern
     Willamette Valley at mid-morning.  Surface winds had shifted
     from southerly to southwesterly along the north coast and in
     the Portland area...in the immediate wake of the front. 
     Doppler radar was showing very light rainfall from SW
     Washington to the northern Oregon Coast and over the
     northern coastal range.  Another area of light rain was
     showing up over the northern Cascade foothills, with local
     upslope conditions enhancing the frontal precipitation. Radar
     also showed showers over extreme north-central and NE Oregon.

     Satellite imagery this morning showed mostly cloudy skies
     across the northern half of Oregon and mostly sunny skies
     over southern Oregon.  The cold front will fall apart as it
     pushes east of the Cascades this afternoon.  Northwesterly
     flow aloft will slowly clear skies over Western Oregon this
     afternoon, but temperatures will only climb into the low to
     mid 70s across the Willamette Valley.  Relative humidties
     should drop below 45% this afternoon, which will aid in the
     drying of damp fields throughout the valley.

     The jet stream will migrate northward overnight, to over
     Southern British Columbia.  A warm front will spread more
     clouds across Western Washington and the northern Willamette
     Valley, but no precipitation is expected east of the north
     coastal range.  Skies should continue to clear overnight
     across the south valley.  Overnight temperatures should be
     near normal with lows in the low to mid 50s.

Surface Winds:
     S 5-12 this morning, NW 5-12 this afternoon.
Transport Winds:
     SW 12 this morning, WNW 8 this afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height today will be near 5000 feet.  Ventilation index 60.
High Temperature:
     Salem\'s high temperature today will be near 74.
Humidities:
     Relative humidity drops to 50% by 1pm.
     Minimum relative humidity will be near 43%.
Sunrise/Sunset:
     Salem sunset tonight: 7:57pm; sunrise tomorrow: 6:30am.

Extended Outlook:
     Flat ridging aloft will send the storm track into Canada and
     dry the air mass over Oregon Thursday with transport winds
     turning northerly.  A stronger upper-level trough is
     forecast to approach the coastline Friday afternoon with the
     flow aloft becoming southwesterly.  That will warm valley
     temperatures well into the 80s with mostly sunny skies.

     Transport winds are forecast to back from northerly to
     northwesterly Friday afternoon with high mixing heights
     ahead of the approaching weather system.  That may create a
     burning opportunity...especially for the north valley. 
     Mechanical fluffing of damp fields is required, if you plan
     to take advantage of the potential Friday afternoon burning
     opportunity.

     A strong upper-level trough is forecast to move over the
     region Saturday with increasing onshore flow cooling valley
     temperatures back into the 70s.  Some drizzle is
     possible...especially along the coast and over the north
     valley.  The upper-level trough will push east of the region
     with the flow aloft turning northwesterly Sunday afternoon. 
     That will begin to clear skies with trasport winds turning
     northerly.

     A transitory ridge is forecast for Monday with temperatures
     recovering to near normal.  Another weather system is
     forecast for Tuesday, which could create a burning
     opportunity, if it holds off until late in the day.  An
     upper-level trough will bring a chance of showers early
     Wednesday with a stronger ridge of high pressure building
     over the region beginning Wednesday afternoon.

Tomorrow (28 Aug):  Mostly Sunny and Warmer.  53/83

Fri (29 Aug):  Mostly Sunny.  Increasing High Clouds Late.  55/83

Sat (30 Aug):  Mostly Cloudy and Much Cooler.  Chance of Drizzle.  55/72

Sun (31 Aug):  Morning Clouds.  Chance of Drizzle.  Afternoon Clearing.  50/74

Mon (01 Sep):  Mostly Sunny.  48/77

Tue (02 Sep):  Increasing Clouds.  Chance of Showers Late...Mainly North.  49/77

Wed (03 Sep):  Chance of Showers Early...Afternoon Clearing.  53/74

ODA Meteorologist
weather at oda.state.or.us