[willamette-fcst] Forecast - Tuesday, January 22nd, 2008

Tue Jan 22 11:59:43 PST 2008

Daily Smoke Management Forecast

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

NOON UPDATE

Issued: 
     Tuesday, January 22nd, 2008 at 12:00pm.

Burn Advisory:
     Agricultural burning is allowed.  Suggested burn times are from now until 3:00pm.
     Straw stack burning is allowed from now until 3:00pm.

Weather Discussion:
     Under clear skies overnight, the dry air mass allowed
     temperatures to rapidly cool to the lowest readings of the
     winter across the Pacific Northwest.   Most of Central and
     Eastern Oregon was near or below zero this morning. 
     Meacham, in Northeast Oregon, dropped to 23 degrees below
     zero for the cold spot in the state.  Burns dipped to 14
     below zero, Redmond bottomed out at 8 below and Pendleton
     dropped to 3 above zero.

     The cold air was continuing to be funneled through the
     Columbia Gorge into the Willamette Valley this morning.  The
     Dalles, at the east end of the gorge, was just 11 degrees
     this morning.  At the west end of the gorge easterly winds
     were gusting to near 40mph at troutdale late this morning
     with temperatures still below freezing.  Portland dropped to
     23 this morning with calmer air in Hillsboro allowing the
     temperatuture to fall to 19 degrees.  Salem dipped to 23,
     Corvallis and Eugene fell to 21.  Below freezing
     temperatures extended to the coastline this morning where
     Astoria fell to 26 degrees and Newport hit 30 with east
     winds gusting to near 30 mph.

     Today will be a repeat of Monday with sunny skies, cool
     temperatures, and strong offshore flow across the state. 
     Highs will climb to near 40 degrees across Western Oregon
     with north to northeast winds.  By late this morning
     temperatures had recovered into the low to mid 30s in the
     Willamette Valley and into the low 40s with easterly winds
     along sections of the coast.  The late-morning ODA surface
     analysis showed strong high pressure centered over the
     Columbia Basin of SE Washington and NE Oregon.  A low
     pressure center was just off the Central California
     Coastline, with an associated low-pressure trough extending
     northward to just off the Oregon Coast.

     Mixing heights today should climb close to 2000 feet, with
     enough of an offshore flow component to the transport winds
     to allow for stack burning.  The air mass over Oregon is
     extremely dry with dew-point temperatures in the teens or
     single digits west of the Cascades and single digits to
     below zero across Central and Eastern Oregon.  With the lack
     of an insulating blanket of snow, frost sensitive crops will
     continue to be in danger, from the cold temperatures, for at
     least the next couple of mornings.

Surface Winds:
     NNE 10-15 this afternoon.
Transport Winds:
     NE  15 this afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height today will be near 1800 feet.  Ventilation index 27.
High Temperature:
     Salem\'s high temperature today will be near 40.
Humidities:
     Minimum relative humidity will be near 32%.
Sunrise/Sunset:
     Salem sunset tonight: 5:06pm; sunrise tomorrow: 7:41am.

Extended Outlook:
     Temperatures will rapidly fall this evening under clear
     skies and continued dry offshore flow.  Wind-sheltered areas
     of the Willamette Valley will likely drop into the upper
     teens Wednesday morning.  A decrease in the offshore flow,
     slighly warmer air aloft, and a full day of sunshine should
     help temperatures climb into the low 40s Wednesday afternoon.

     Under clear skies, temperatures will rapidly fall back into
     the 20s Wednesday night.  A weather system is forecast to
     drop southeastward from the Gulf of Alaska to just off the
     Oregon Coast by Thursday afternoon.  That will maintain the
     surface offshore flow and keep low-level cold air in place
     across Western Oregon, while increasing southwesterly flow
     aloft feeds Pacific moisture over the cold dome.

     This is a classic set-up for snow across Western Oregon for
     Thursday afternoon.  The limiting factor will be the amount
     of moisture forecast to spread inland.  At this time, it
     appear that snowfall will be light with the greatest chance
     for accumulating snow in the central and southern sections
     of Western Oregon.  The bulk of the moisture is expected to
     stay offshore, as the system moves southward along the
     Oregon Coast, then dives southeastward into Northern California.

     Skies should begin to clear over the Willamette Valley
     Thursday night with low-level cold air still in place across
     all of Oregon. Friday appears to be a break-day from any
     storm activity with mostly sunny skies and cool temperatures again.

     The forecast gets very tricky after Friday with a stronger
     system forecast by all the computer models to drop
     southeastward from the Gulf of Alaska into the Pacific
     Northwest.  With low-level cold air still in place across
     Western Oregon, the precipitation should at least begin as
     snow near midday Saturday.  How long it stays as snow will
     depend on the exact track of the incoming system and is too
     far out to call at this time.  It appears that there will be
     enough onshore flow, with the passage of the cold front
     Saturday afternoon, to transition the snow to rain across
     the lower elevations of Western Oregon, but the snow levels
     will ramin low enough for heavy snow in the coast range and
     Cascades.

     A cold upper-level trough is forecast to move over the
     region Sunday and Monday for showery conditions with very
     low snow levels.  Sticking snow above 500 feet, at times, is
     a real possibility, with a threat of sticking snow again on
     the valley floor.  Another cold system may bring more rain
     or snow to the region Tuesday.

Tomorrow (23 Jan):  Sunny.  18/41

Thu (24 Jan):  Increasing Clouds.  Chance of Light Snow...Mainly South.  22/37

Fri (25 Jan):  Mostly Sunny and Cool.  25/40

Sat (26 Jan):  Snow...Likely Changing to Rain in the Afternoon.  28/42

Sun (27 Jan):  Showers of Rain or Snow.  Possible Significant Accumulations.  33/37

Mon (28 Jan):  Showers of Rain or Snow.  Possible Significant Accumulations.  32/37

Tue (29 Jan):  Showers of Rain or Snow.  Possible Significant Accumulations.  32/37

ODA Meteorologist
weather at oda.state.or.us