[willamette-fcst] Forecast - Wednesday, April 8th, 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, April 8th, 2009 at 9:00am.

Burn Advisory:
     Agricultural burning is allowed.  Suggested burn times are from now until 6:00pm.
     Straw stack burning is allowed from now until 6:00pm.

Weather Discussion:
     An upper-level low-pressure system moved onshore into
     central California Tuesday night and was continuing east
     into Nevada this morning.  Satellite imagery showed cloudy
     skies circulating around it covering most of Oregon. 
     Doppler radar showers most of the shower activity confined
     to east of the Cascades, with significant rainfall over
     portions of south-central Oregon.  Lakeview received almost
     one-half inch of rain overnight with over a tenth of an inch
     in Klamath Falls.

     Some sprinkles also fell overnight along the coast and in
     the Willamette Valley, extending as far north as Salem this
     morning.  North Bend, on the south coast, did received
     almost a tenth of an inch of rain, but most spots in western
     Oregon reported only trace amounts.  East of the Cascades,
     areas of light rain extended northward to Meacham, in
     northeast Oregon, this morning.

     The main effect the storm was a strong influx of marine air
     Tuesday evening across western Oregon.  That capped high
     temperatures Tuesday afternoon in the mid 60s in the south
     valley, but the Portland area managed to reach the mid 70s,
     for the second day in-a-row, before the cooler marine air
     began invading the north valley. Cloudy skies overnight held
     temperatures in the mid 40s to low 50s across western Oregon.

     The Salem sounding this morning showed massive cooling aloft
     compared with Tuesday afternoon.  The freezing level had
     dropped from 9600 feet down to 5200 feet, and the air mass
     had become quite moist.  Colder air aloft and southwesterly
     transport winds will make for excellent ventilation
     conditions across western Oregon today.  The ODA surface
     analysis had a classic post marine-push pattern with onshore
     flow and the strongest pressure gradients over central and
     eastern Oregon.  Westerly winds gusting over 30 mph were
     ushering cooler marine air across the eastern half of the
     state, with lighter southwesterly winds in the Willamette Valley.

     Skies should stay mostly cloudy today across western Oregon,
     with a chance of sprinkles, as strong onshore flow
     continues.  Temperatures will be near to slightly below
     normal with highs only in the mid to upper 50s.  Showers
     will continue over the eastern portions of the state, as the
     upper-level low-pressure system moved into Idaho.

Surface Winds:
     SW 5-15 this morning, SW 5-15 this afternoon.
Transport Winds:
     SW 15 this morning, SW 15 this afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height today will be near 4200 feet.  Ventilation index 63.
High Temperature:
     Salem\'s high temperature today will be near 57.
Humidities:
     Minimum relative humidity will be near 62%.
Sunrise/Sunset:
     Salem sunset tonight: 7:49pm; sunrise tomorrow: 6:38am.

Extended Outlook:
     The next weather system is forecast to weaken as it moves
     onshore Thursday but will likely be strong enough to bring
     some showers to most of western Oregon.  A weak westerly
     flow aloft is forecast for the remainder of the week,
     bringing lots of clouds and seasonal temperatures.

     The latest computer guidance is still uncertain on the
     timing of a stronger system slated to move onshore sometime
     between Sunday afternoon and Monday morning, with a cool and
     unsettled pattern forecast for early next week.

Tomorrow (09 Apr):  Showers Likely.  Snow Level Dropping to 4000 Feet.  42/54

Fri (10 Apr):  Mostly Cloudy.  Chance of Light Showers.  40/55

Sat (11 Apr):  Becoming Mostly Cloudy.  Chance of Showers.  40/57

Sun (12 Apr):  Increasing Clouds.  Chance of Rain.  Snow Level Dropping to 3000 Feet.  40/57

Mon (13 Apr):  Showers Likely.  Snow Level 2500 Feet.  42/54

Tue (14 Apr):  Decreasing Showers.  Snow Level 2500 Feet.  37/55

Wed (15 Apr):  Mostly Cloudy.  Slight Chance of Showers.  38/59

ODA Meteorologist
weather at oda.state.or.us