[willamette-fcst] Forecast - Monday, March 8th, 2010

[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: 
     Monday, March 8th, 2010 at 9:00am.

Burn Advisory:
     Recommended burn times for agricultural burning are from now until 4:00pm.
     Stack burning is allowed from now until 4:00pm.

Weather Discussion:
     After a sunny and mild Saturday, with afternoon highs climbing into the mid 60s in the
     Willamette Valley, an active cold front brought cloudy skies and cooler temperatures back
     to western Oregon Sunday. High temperatures were held in the mid 50s, with rain moving
     onshore during the afternoon.  Rain spread across western Oregon Sunday evening, with
     the snow level dropping from 5-6000 feet, Sunday evening, to near 2000 feet by early this
     morning.  CoCoRaHS reports indicated that between one-tenth and one-third of an inch of
     rain fell across the Willamette Valley overnight, with a couple of inches of snow falling
     on the Cascade passes.

     The cold front was bringing areas of light rain and snow to eastern Oregon this morning.
     Dry northwesterly onshore flow flow had cleared skies considerably across northwestern
     Oregon, but an upper-level disturbance off the southern Oregon coast was keeping skies
     cloudy across southwestern Oregon with areas of rain and mountain snow.  Colder air
     aloft, in the wake of the cold front, had lowered the freezing levels over Salem and
     Medford to just 2800 feet and 3800 feet respectively by early this morning.  ODOT road
     cameras, over the Cascade passes, showed snow-covered roads this morning with temperatures
     in the mid to upper 20s.

     The surface cold front will continue eastward, into Idaho, this afternoon.  The offshore
     cold upper-level trough is showing signs of splitting apart, with the bulk of the cold
     pool aloft headed towards northern California.  That will keep post-frontal showers to a
     minimum across northwestern Oregon this afternoon, but afternoon heating will act to
     destabilize the atmosphere and likely produce at least some shower activity...mainly over
     the mountains.

     Even with the higher March sun-angle and some sunshine today, the coldest air aloft so
     far in 2010, will keep high temperatures near 50 degrees across the Willamette Valley today.
     The snow level could drop as low as about 1000 feet in the heavier showers.  There is also
     a slight chance of an afternoon thunderstorm.  High mixing heights and northwesterly winds
     will make for excellent ventilation conditions across western Oregon today. 

Surface Winds:
     NW 5-15 this morning, NW 10-15 G20 this afternoon.
Transport Winds:
     N 15 this morning, NNW 15 this afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height today will be near 5500 feet.  Ventilation index 83.
High Temperature:
     Salem\'s high temperature today will be near 49.
Humidities:
     Minimum relative humidity will be near 44%.
Sunrise/Sunset:
     Salem sunset tonight: 6:09pm; sunrise tomorrow: 6:35am.

Extended Outlook:
     A transitory ridge of high pressure will bring clearing skies tonight.  With a cold air
     mass over the region, sub-freezing temperatures are likely across the western valleys.
     Tender vegetation may need protection.  Another cold weather system will quickly move
     onshore Tuesday, with more rain and mountain snow in the afternoon.  Significant
     accumulations of snow are likely over the Cascade passes and possibly the coastal range
     passes.  Valley highs will be held in the upper 40s Tuesday with increasing rain.

     Showers will continue into Wednesday morning, with western valley temperatures dropping
     into the mid 30s and snow levels lowering to around 1000 feet.  Some clearing and warming
     aloft will help temperatures recover into the lower 50s Wednesday afternoon.  Thursday
     appears to be a break from the wet weather, with the next system coming onshore Thursday
     night and Friday.  Another cold upper-level trough, with very low snow levels, is forecast
     to follow the front onshore Friday night and Saturday.  An upper-level ridge is forecast to
     bring some clearing Sunday, which could lead to another frosty morning.  More warming is
     forecast for Monday.

Tue (09 Mar):  Frosty Start. Rain Developing in the Afternoon. Snow Level 1500 Feet. 30/48

Wed (10 Mar):  Rain Turning to Showers.  Snow Level Near 3000 Feet.  34/52

Thu (11 Mar):  Partly Sunny.  Increasing Rain Late.  Snow Level Rising To 5000 Feet.  36/55

Fri (12 Mar):  Rain Turning to Showers. Snow Level Dropping Below 2500 Feet.  40/52

Sat (13 Mar):  Showers.  Snow Level 2-3000 Feet.  36/52

Sun (14 Mar):  Cool Start...Becoming Partly Sunny.  32/55

Mon (15 Mar):  Mostly Sunny.  Increasing Clouds Late.  36/60

ODA Meteorologist
weather at oda.state.or.us