[willamette-fcst] Forecast - Wednesday, February 11th, 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 11th, 2009 at 9:00am.

Burn Advisory:
     Agricultural burning is allowed.  Suggested burn times are from now until 3:30pm.
     Stack burning is not allowed.

Weather Discussion:
     A cool weather system, from the Gulf of Alaska, brought rain
     and snow to the region Tuesday, with the snow level
     initially near the valley floors.  The snow level lifted to
     about 1500 feet overnight, and the precipitation tapered
     off.  Skies were mostly cloudy overnight with occasional
     showers across western Oregon. Temperatures stayed above
     freezing with valley minimums in the mid to upper 30s.

     Satellite imagery and surface reports showed the
     low-pressure center, off the southern Oregon coast, 
     continuing to slowly drift southeastward.  A fairly
     impressive cloud-shield, wrapping around it, spread across
     most of Oregon.  Doppler radar showed numerous showers,
     rotating northward, from northern California to Portland,
     Oregon.  As the low-pressure center slowly weakens and comes
     onshore, near the Oregon/California border this afternoon,
     shower activity should taper off, from north to south,
     across Oregon.  Temperatures will stay below normal, with
     valley highs only near 45 degrees (normal would be in the
     low 50s).

     The air mass is slowly warming over the region.  The morning
     soundings measured the freezing levels over Salem and
     Medford at 2900 and 3500 feet respectively.  Another few
     inches of snow are possible today, above about 2000 feet,
     before the showers taper off tonight.  Showers will be most
     numerous across sotuhwestern Oregon.  Transport winds this
     morning were southeasterly and should back to northeasterly,
     as the low-pressure system continues to move south and east.
      Northeasterly transport winds are not favorable for stack
     burning, so it is not allowed today.

     Plan on continued winter driving conditions over mountain
     passes above 1500 feet today and tonight.  ODOT road cameras
     showed wet pavement with areas of slush over the coastal
     passes and packed snow over the Cascade passes. 
     Temperatures have remained just warm enough in the Columbia
     Gorge to avoid significant snow accumulation at river-level,
     where travel conditions appeared okay this morning.  Skies
     should begin to clear tonight, which will allow many areas
     in the valley and in the Gorge to fall below freezing by
     Thursday morning.  Some road surfaces could become slick, so
     travel with caution overnight and early Thursday. There may
     also be areas of fog formation overnight in the Willamette Valley. 

Surface Winds:
     NE 5-15 this morning, N 5-15 this afternoon.
Transport Winds:
     E 12 this morning, NE 12 this afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height today will be near 2000 feet.  Ventilation index 24.
High Temperature:
     Salem\'s high temperature today will be near 46.
Humidities:
     Minimum relative humidity will be near 60%.
Sunrise/Sunset:
     Salem sunset tonight: 5:35pm; sunrise tomorrow: 7:17am.

Extended Outlook:
     The next weather system, in this latest series of cool
     storms from the Gulf of Alaska, is forecast to take a
     slightly more of a southerly track, but it should bring more
     rain and snow to western Oregon late Thursday and Friday. 
     With increasing offshore flow, the snow level may drop to
     around 500-1000 feet early Friday, with accumulation snow
     likely again over the coastal and Cascade passes.  Some wet
     snow may locally mix to the valley floors, but significant
     accumulations below 1000 feet are not expected.  The bulk of
     the moisture from this system will move into southwestern
     Oregon and northern California.

     The next weather system is forecast to take an even more
     southerly track, Sunday and Monday, with the bulk of the
     moisture staying south of Oregon.  That will maintain a cool
     offshore low-level flow across western Oregon, so
     temperatures will stay well below normal with low snow
     levels.  the next system is forecat to come onshore Tuesday,
     and that one may also be directed mainly into California.

Thu (12 Feb):  Increasing Clouds. Chance of PM Rain. Snow Level Dropping to 1000 Feet.  28/45

Fri (13 Feb):  Decreasing Rain and Snow.  Snow Level Near 1000 Feet.  33/44

Sat (14 Feb):  Partial Clearing and Cool.  Slight Chance of a Shower.  30/47

Sun (15 Feb):  Chance of Showers and Cool.  Snow Level Near 2000 Feet. 30/47

Mon (16 Feb):  Mostly Cloudy.  Slight Chance of Showers.  Snow Level 2500 feet.  32/48

Tue (17 Feb):  Increasing Chance of Rain.  Snow Level 2-3000 Feet.  33/48

Wed (18 Feb):  Chance of Showers.  Snow Level 3000 Feet.  36/50

ODA Meteorologist
weather at oda.state.or.us