[willamette-fcst] Forecast - Wednesday, February 25th, 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, February 25th, 2009 at 9:00am.

Burn Advisory:
     Agricultural burning is allowed.  Suggested burn times are from 9:00am until 4:00pm.
     Straw stack burning is allowed, for dry stacks, from 9:00am until 4:00pm.

Weather Discussion:
     A strong and moist west-southwesterly flow aloft continued
     the shower activity across Washington and Oregon overnight. 
     With the showery nature of the precipitation, there was a
     wide variety of rainfall amounts over the past 24 hours. 
     Some coastal and inland valley locations, such as Newport
     and McMinnville, received only around one-tenth of an inch,
     while other areas, like North Bend and Eugene, picked over
     over one inch of rain.  Cloudy and rainy conditions kept
     overnight temperatures in the 40s across the lower
     elevations of western Oregon.

     Snow levels remained around 4000 feet, in the Cascades
     overnight, with about an inch of new snow on the passes this
     morning.  Significant amounts of snow have fallen in the
     higher elevations on Mt. Hood.  Timberline lodge reported 12
     inches of new snow in the past 24 hours and 52 inches of new
     snow in the past 72 hours.  That is a welcome site, for the high
     country, after drier than normal conditions since early January.

     The moist west-southwesterly flow off the Pacific Ocean will
     strengthen today, as a cold upper-level low pressure area
     drops southward, from southern British Columbia, to off the
     northern Washington Coast.  Satellite imagery showed cloudy
     skies across virtually all of Washington and Oregon at
     mid-morning.  Doppler radar showed bands of showers rotating
     inland and across the entire region.  Showers were even
     making it east of the Cascades, especially over higher terrain.

     With little or no sunbreaks today, and progressively cooler
     air aloft moving over the region, temperatures will only
     warm a couple of degrees from their current levels.  Valley
     highs should top out near 50 degrees, down a few degrees
     from yesterday, with frequent showers.  Ventilation
     conditions will be good today, but straw stacks may loaclly
     be too wet for burning.  The Cascades will see around 5-10
     inches of new snow, above 3500 feet, where Winter Weather
     Advisories are in effect.

Surface Winds:
     SW 5-15 this morning, SW 10-15 G25 this afternoon.
Transport Winds:
     SW 20 this morning, SW 30 this afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height today will be near 3900 feet.  Ventilation index 117.
High Temperature:
     Salem\'s high temperature today will be near 50.
Humidities:
     Minimum relative humidity will be near 66%.
Sunrise/Sunset:
     Salem sunset tonight: 5:55pm; sunrise tomorrow: 6:55am.

Extended Outlook:
     A cold upper-level low-pressure system is forecast to
     continue to slowly sag southward, along the Washington
     Coast, tonight.  That will increase the showers and
     southwesterly winds across western Oregon with snow levels
     lowering to at or below 1000 feet by Thursday morning. 
     Another 5-10 inches of snow could fall in the Cascades
     overnight with 2-4 inches of snow possible over the coastal
     mountain passes.

     As the very cold upper-level low-pressure system swings
     onshore Thursday, wet snow accumulations are also possible
     in the higher hills around the Willamette Valley.  Showers
     could mix with or turn to snow even down to the Willamette
     Valley Floors.  The best chance for sticking snow on the
     valley floors appears to be early Thursday.  Significant
     accumulations are not expected below 500 feet, but wet snow
     could locally cover the ground under heavier showers.  High
     temperatures should still climb into the mid 40s Thursday
     afternoon, with brisk southwesterly winds.  The mountains
     will likely see an additional 2-7 inches of snow.

     The upper-level low-pressure system is forecast to move east
     of the Cascades Thursday night with showers tapering off and
     skies clearing.  That will allow for much colder overnight
     temperatures.  Valley minimums will likely drop to near or
     below freezing.  A transitory ridge of high pressure may
     bring a mostly dry, but quite cool, day Friday, with a touch
     of sunshine.

     The next weather system is forecast to develop further
     offshore, with increasing southwesterly flow aloft briefly
     lifting snow levels to near the Cascade passes Saturday
     afternoon.  That system is forecast to move onshore with
     rain and blustery winds Saturday night and Sunday.  Snow
     levels should drop back below the Cascade passes Sunday. 
     Showers will continue Monday and Tuesday with snow in the
     mountains.  Another cool weather system is forecast to drop
     into the region, from the Gulf of Alaska, on Wednesday.

Tomorrow (26 Feb):  Showers.  Snow Level near 500 Feet.  37/44

Fri (27 Feb):  Partly Sunny and Cool.  Slight Chance of a Shower.  30/50

Sat (28 Feb):  Increasing Clouds.  Chance of PM Rain.  Snow Level Rising to 4000 Feet.  31/49

Sun (01 Mar):  Rain.  Snow Level Dropping to 3000 Feet.  39/52

Mon (02 Mar):  Showers.  Snow Level  Near 3000 Feet.  37/50

Tue (03 Mar):  Mostly Cloudy.  Chance of Showers.  Snow Level near 4000 Feet.  36/52

Wed (04 Mar):  Rain Increasing.  Snow Level 4000 Feet.  36/52

ODA Meteorologist
weather at oda.state.or.us