[willamette-fcst] Forecast - Thursday, February 19th, 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, February 19th, 2009 at 9:00am.

Burn Advisory:
     Agricultural burning is allowed.  Suggested burn times are from 11:00am until 4:00pm.
     Stack burning is not allowed.

Weather Discussion:
     Fair skies and light winds overnight allowed temperatures,
     once again, to drop near or below freezing across the
     Willamette Valley.  Hillsboro dipped to 28 degrees, Salem
     dropped to 30 and Portland 31.  An upper-level low pressure
     center continues to be anchored several hundred miles off
     the northern California coastline this morning.  Satellite
     imagery showed an impressive cloud-shield circulating around
     it, with all of the precipitation staying well offshore. 
     Middle and high clouds were spreading northward across
     Oregon and Washington.  There were also areas of fog and low
     clouds this morning in the southern Willamette Valley and
     east of the Cascades.    

     Counter-clockwise circulation around the offshore weather
     system is producing southwesterly flow aloft over Oregon and
     warming the air mass.  The freezing level over Salem had
     climbed from 5200 feet yesterday morning to 7500 feet this
     morning.  Warm air aloft will keep mixing heights below
     about 1500 feet today.  Transport winds are expected to
     remain fairly light and mostly from the northeast, so stack
     burning is not allowed.

     The ODA surface analysis showed a little stronger offshore
     pressure gradients across western Oregon, compared with
     yesterday morning. Easterly winds were were blowing around
     5-15 mph along the coast at mid-morning with generally calm
     winds in the Willamette Valley.  Mid-mornig temperatures
     were in the low to mid 30s in the Willamette Valley but had
     already warmed into the mid 40s along the coast at Newport
     and North Bend.  Skies were mostly cloudy with some fog in
     the Eugene area.

     Like yesterday, the fog should clear later this morning, but
     there will still be considerable middle and high clouds
     filtering the late-winter sunshine.  Willamette Valley
     temperatures should climb mostly into the mid and upper 50s
     this afternoon (most areas will be a degree or two warmer
     than yesterday). Surface winds will remain lightly offshore.

Surface Winds:
     NNE 3-6 this morning, NE 3-7 this afternoon.
Transport Winds:
     NNE 6 this morning, NE 7 this afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height today will be near 1500 feet.  Ventilation index 11.
High Temperature:
     Salem\'s high temperature today will be near 58.
Humidities:
     Minimum relative humidity will be near 36%.
Sunrise/Sunset:
     Salem sunset tonight: 5:46pm; sunrise tomorrow: 7:04am.

Extended Outlook:
     There will continue to be considerable middle and high
     cloudiness filtering the sunshine across Oregon Friday and
     Saturday.  The air mass will continue to be mild with
     temperatures running a couple of degrees above normal in
     most areas.  As the storm off the California coastline
     slowly moves eastward, the chance of rain will increase
     significantly by Saturday night.

     An upper-level low pressure system will finally move close
     enough to the coastline by Sunday for a good chance of light
     rain across western Oregon.  Temperatures will remain mild
     with increasing southwesterly flow aloft.  A cold front is
     forecast to finally move across western Oregon Sunday night
     or Monday with a showery and cooler weather pattern setting
     up for much of next week.  Snow levels will drop
     dramatically by the middle of next week, with considerable
     new snow possible over the Cascade passes.  Colder air aloft
     should improve ventilation conditions across western Oregon.

Tomorrow (20 Feb):  Areas of AM Fog.  Mostly Cloudy and Mild in the Afternoon.  32/57

Sat (21 Feb):  Areas of AM Fog.  Mostly Cloudy and Mild in the Afternoon.  34/57

Sun (22 Feb):  Rain Likely.  Snow Level 5-6000 Feet.  38/53

Mon (23 Feb):  Rain Likely at Times.  Snow Level 5000 Feet...Dropping late.  40/50

Tue (24 Feb):  Showers.  Mountain Snow.  Snow Level 3000 Feet.  38/50

Wed (25 Feb):  Showers.  Mountain Snow.  Snow Level 3000 Feet.  37/49

Thu (26 Feb):  Showers.  Mountain Snow.  Snow Level 2000 Feet.  36/48

ODA Meteorologist
weather at oda.state.or.us