[willamette-fcst] Forecast - Tuesday, March 3rd, 2009

Tue Mar 3 09:08:09 PST 2009

Daily Smoke Management Forecast

Oregon Department of Agriculture
Smoke Management Program
Weather Outlook and Field Burning Advisory for Willamette Valley Growers and Fire Districts.

...Next Update Not Until Wednesday, March 4th at 9:00am...

Issued: 
     Tuesday, March 3rd, 2009 at 9:00am.

Burn Advisory:
     Agricultural burning is allowed.  Suggested burn times are from now until 4:00pm.
     Straw stack burning is allowed from now until 4:00pm.

Weather Discussion:
     Another surge of showers rotated onshore, late Monday,
     around a strong upper-level low-pressure system off the
     Oregon and California Coast.About one-quarter of an inch of
     rain fell in the Willamette Vally overnight, with one-tenth
     to one-half inch of rain also scattered across central and
     eastern Oregon.  The air aloft is slowly cooling, as the
     parent upper-level trough moves closer to the coatline.  The
     freezing levels over Salem and Medfor were measured this
     morning at just 4300 feet and 4500 feet respectively.  Snow
     levels dropped below the Cascade passes overnight with a
     couple of inches of new snow falling on the roadways.

     The main jet stream is aimed at central and southern
     California this morning with southwesterly flow aloft
     continuing over Oregon.  Satellite imagery showed mostly
     cloudy skies across the state with far fewer sunbreaks than
     yesterday morning.  Doppler radar showed the strongest
     showers rotating into northern and central California, but
     scattered showers were making their way across all of Oregon
     and Washington.

     Clouds and showers held overnight temperatures mostly in the
     low 40s across western Oregon.  Mid-morning temperatures
     ranged fromt he upper 30s to the mid 40s with partly to
     mostly cloudy skies.  Daytime heating should act to increase
     the shower acticity this afternoon.  There is also a slight
     chance of a thundershower.  Colder air aloft will cap high
     temperatures in the low to mid 50s this afternoon.  The ODA
     surface analysis continued to show south-sooutheasterly
     pressure gradients, and valley winds were in the 5-15 mph
     range at mid-morning.  Winds could gust to around 20 mph
     today...especially near showers.

     A few more breaks in the clouds tonight, along with colder
     air aloft, should valley minimums to drop into the mid 30s,
     but most areas will likely stay just above freezing.  There
     will still be a chance of showers, but it does not appear as
     if an organized impulse of showers will be moving onshore.

Surface Winds:
     SSE 5-15 this morning, SSE 5-15 G20 this afternoon.
Transport Winds:
     S 15 this morning, S 20 this afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height today will be near 5000 feet.  Ventilation index 100.
High Temperature:
     Salem\'s high temperature today will be near 53.
Humidities:
     Minimum relative humidity will be near 56%.
Sunrise/Sunset:
     Salem sunset tonight: 6:03pm; sunrise tomorrow: 6:44am.

Extended Outlook:
     An upper-level trough will weaken slightly Wednesday but
     remain close enough to the coastline to produce some showers
     across Oregon. Snow levels should remain fairly low, with a
     few more inches of snow likely over the Cascade passes. 
     Valley highs Wednesday will likely cool a couple of more
     degrees from today.

     A quite cold system is forecast to drop into the region,
     from southern British Columbia, Thursday afternoon and
     Friday.  This system is now expected to take a slightly more
     eastern track than previously forecast, which will limit the
     amount of cold air and moisture dropping into Oregon.  It will
     still increase showers and lower snow levels across the region.

     Showers will taper off early Friday, with snow levels likely
     lifting to 3000 feet.  we may see a brief break in the
     weather Saturday morning, before another very cold system
     drops into the region Saturday night and Sunday.  That
     system is forecast to be even colder than the one Thursday
     night, so it has the potential to bring wet snow to the
     lower elevations of northwestern Oregon by sunday morning.

Tomorrow (04 Mar):  Showers...Decreasing Late.  35/50

Thu (05 Mar):  Increasing Showers and Cooler.  Snow Level Dropping to 2000 Feet.  34/47

Fri (06 Mar):  Showers Ending.  Partly Sunny.  Snow Level Rising to 3000 Feet.  32/47

Sat (07 Mar):  Partly Cloudy.  Increasing Chance of Showers PM.  31/50

Sun (08 Mar):  Increasing Rain and Snow.  Wet Snow Possible on the Valley Floor.  33/44

Mon (09 Mar):  Rain or Snow Showers Ending.  Partly Sunny and Quite Cool.  30/46

Tue (10 Mar):  A Frosty Morning...Becoming Mostly Sunny and a Little Warmer.  29/50

ODA Meteorologist
weather at oda.state.or.us