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

[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: 
     Tuesday, January 22, 2008 at 4:45 pm.

Burn Advisory For Wednesday, January 23, 2008:
     Agricultural burning is not recommended.
     Stack burning is not allowed.

Weather Discussion:
     This morning was the coldest so far this winter for much of
     Oregon.  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 Dalles, at the east end of the
     gorge, was just 11 degrees this morning.  West of the
     Cascades, Portland dropped to 23 this morning and Hillsboro
     was 19 degrees.  Salem dipped to 23, while Corvallis and
     Eugene fell to 21.  Even the coastline was cold with Astoria
     starting out at 26 degrees and Newport 30 with east winds
     gusting to near 30 mph.

     Today was a repeat of Monday with sunny skies, cool
     temperatures, and strong offshore flow across the state. 
     Highs generally climbed into the low 40s across the
     Willamette Valley.  The coast was warmer with easterly winds
     yielding another bright and sunny day.  Afternoon
     temperatures ranged from the low 40s along the north coast
     to the 50s south of about Coos Bay.  It remained well below
     freezing east of the Cascades this afternoon, with 28
     degrees at Redmond being one of the warmer spots.  Pendleton
     managed to creep into the low 20s, while Baker City strugled
     to reach 11 degrees.  La Grande topped out at 14.  The
     Dalles crept up to 33 degrees.

     The late-afternoon ODA surface analysis showed strong high
     pressure centered over NE Oregon and a low perssure trough
     along the Oregon Coast.  That combination of pressure
     systems was responsible for the offshore flow across the
     state again today...although it was a bit weaker for maost
     areas than on Monday.  The exception to that was in the
     Columbia Gorge, where east winds increased in strength
     today...continuing to push cold air from the Columbia Basin
     into Western Oregon.  Troutdale, near the western end of the
     gorge, only managed to reach 35 degrees this afternoon with
     east winds gusting over 35 mph at times and windchill values
     near 20 degrees.  

     The freezing level over salem rose from the surface this
     morning to 4300 feet this afternoon.  Mixing heights rose to
     about 2000 feet this afternoon but ventilation conditions
     will deteriorate tomorrow as continued warming aloft
     strengthens a low-level temperature inversion over Western
     Oregon.  That is why stack burning is not allowed
     Wednesday.

     Temperatures will rapidly fall this evening under clear
     skies and continued dry offshore flow.  Wind-sheltered areas
     of the Willamette Valley will see overnight lows drop into
     the upper teens.  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.

     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.  


Surface Winds:
     N-NE 5-10 Wednesday morning, N-NE 5-15 Wednesday afternoon.
Transport Winds:
     NE 5-10 Wednesday morning, NE 10-15 Wednesday afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height Wednesday will be near 1500 feet.  Ventilation index 8.
High Temperature:
     Salem\'s high temperature Wednesday will be near 42.
Humidities:
     Minimum relative humidity will be near 40%.
Sunrise/Sunset:
     Salem sunrise Wednesday: 7:41 am; sunset Wednesday: 5:07 pm.

Extended Outlook:
     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...especially in the coastal range.  It is
     possible that the Willamette Valley could pick up an inch or
     two of snow, if enough moisture circulates that far inland. 
     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 temperature
     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. It appears
     that there will be enough onshore flow, with the passage of
     the cold front Saturday afternoon, to change the snow to
     rain across the lower elevations of Western Oregon, but the
     snow levels will remain low enough for heavy snow in the
     coast range and in the Cascades.

     A couple of very cold upper-level troughs are forecast to
     move over the region Sunday through Wednesday for showery
     conditions with very low snow levels.  Sticking snow above
     500 feet, at times, is a real possibility, with a threat of
     wet sticking snow on the valley floor at times.

Wed (23 Jan):  Sunny.  18/42

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

Wed (30 Jan):  Showers of Rain or Snow.  Possible Significant Accumulations.  32/37

ODA Meteorologist
weather at oda.state.or.us