[willamette-fcst] Forecast - Monday, March 9th, 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: 
     Monday, March 9th, 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:
     A weather system dropped straight down the British Columbia
     Coastline and directly into Washington and Oregon Saturday.
     that brought light rain to western Oregon with rainfall
     amounts ranging from a few hundredths to about one-quarter
     of an inch.  Snow levels never rose above about 2000 feet,
     with a few inches of new snow falling in the Cascades.  A
     very cold upper-level trough followed the cold front
     Saturday night and Sunday, with instability showers falling
     as snow all the way down to sea level.  Accumulations were
     light, on the valley floor, with most areas just seeing a
     light dusting that did not stick on the road surfaces.

     Another 3-7 inches of snow fell in the Cascades Sunday, with
     a couple of inches also reported over the coastal mountain
     passes.  Total snowfall over the weekend locally exceeded a
     foot in sections of the Cascades.  With some rain-shadow
     effects over the western valleys, much of the Willamette
     Valley had at least a little sunshine Sunday afternoon. 
     However, with the very cold air mass in place across the
     region, high temperatures were only in the low to mid 40s
     (about 10-12 degrees below normal).

     Another upper-level disturbance, in a cold
     north-northwesterly flow aloft, was dropping sothward, from
     sotuhern British Columbia, this morning.  It was acting to
     increase shower activity across western Washington and
     northwestern Oregon, with snow levels continuing near sea
     level.  Scattered light rain and snow showers were falling,
     across the Willamette Valley this morning, with some snow
     mixing with the rain even along the northern and central
     Oregon Coast.  Showers will increase later this morning, as
     the upper-level disturbance drops into northern Oregon. 
     Daytime heating will lift the snow level to around 500-1000
     feet by this afternoon, but snow could continue to mix down
     to sea level with heavier showers.  Some showers could also
     produce small hail.

     Expect winter driving conditions over the coast range and
     Cascade passes, through early Tuesday.  ODOT reports showed
     snow over all the mountain passes this morning.  Another
     couple of inches of snow are likely over the coastal passes
     today with 3-6 inches of new snow over the Cascade passes. 
     Snow accumulations should be less than 1 inch in the
     Willamette Valley this morning, before the showers at least
     mix with rain this afternoon.

     Valley temperatures were near their minimums at mid-morning
     (in the low to mid 30s). Doppler radar showed one line of
     showers just moving through the valley and another, stronger
     line of showers, coming over the coast range.  The Portland
     Airport was reporting light rain, with a temperature of 36
     degrees, but McMinnville and Salem were seeing light snow
     showers, with temperatures just above freezing.  Some light
     snow showers were beginning to move into the south valley,
     from Corvallis to Eugene, where temperatures were near the
     freezing mark.

     The ODA surface analysis showed a weak trough of low
     pressure just moving onto the coastline and inducing
     southerly winds, around 10-20 mph, in the Willamette Valley.
     That trough, along with the associated upper-level
     disturbance, is forecast to move into northeastern Oregon
     this afternoon.  That will turn surface and transport winds
     more westerly, with showers beginning to decrease this
     evening across western Oregon.

     An Arctic cold front was hleping to enhance the light
     snowfall along a line from Spokane to Seattle, Washington,
     at mid-morning.  Northerly winds, on the north side of that
     front, were ushering below freezing air into the northern
     third of Washington.  That front is expected to stall and
     weaken, across central Washington, later today.

Surface Winds:
     S 5-15 G20 this morning, WSW 10-20 this afternoon.
Transport Winds:
     SW 15 this morning, W 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 44.
Humidities:
     Minimum relative humidity will be near 60%.
Sunrise/Sunset:
     Salem sunset tonight: 7:11pm; sunrise tomorrow: 7:33am.

Extended Outlook:
     Rain and snow showers should taper off tonight with
     gradually clearing skies across western Oregon.  That will
     allow Willamette Valley temperatures to drop into the 20s
     with local record cold minimums possible.  An upper-level
     ridge is forecast to bring a dry and cool northwesterly flow
     aloft to Oregon Tuesday.

     As the ridge builds into the coastline Wednesday,
     temperatures will begin to moderate, after another chilly
     morning, with near-record low temperatures. Surface winds
     will turn offshore Wednesday and strongly offshore Thursday,
     as the upper-level ridge builds directly over Oregon. 
     Afternoon temperatures will continue to warm ,under mostly
     sunny skies, Thursday and Friday, but mornings will continue
     to be quite chilly.

     The next weather system will bring a chance of showers back
     to the region Saturday, under a cooler northwesterly flow
     aloft.  Another Upper-level ridge is forecast to bring
     mostly sunny skies and moderating temperatures Sunday and Monday.

Tomorrow (10 Mar):  A Frosty Morning...Partly Sunny and Cool.  27/47

Wed (11 Mar):  Near Record-Cold Morning.  Mostly Sunny in the Afternoon.  25/50

Thu (12 Mar):  Mostly Sunny and Warmer.  30/55

Fri (13 Mar):  Mostly Sunny and Warmer.  31/58

Sat (14 Mar):  Chance of Showers. Snow Level 3-4000 Feet.  35/50

Sun (15 Mar):  Partly Cloudy.  35/55

Mon (16 Mar):  Mostly Sunny and Warmer.  36/59

ODA Meteorologist
weather at oda.state.or.us