[willamette-fcst] Forecast - Tuesday, December 2nd, 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, December 2nd, 2008 at 9:00am.

Burn Advisory:
     Agricultural burning is allowed.  Suggested burn times are from now until 2:30pm.
     Straw stack burning is allowed from now until 2:30pm.

Weather Discussion:
     A fast-moving cold front swept across western Oregon
     overnight and was near the Idaho border by mid-morning.  The
     strom was stronger across the northern half of the state. 
     Rainfall totals along the coast ranged from about
     one-quarter of an inch at North Bend and Brookings to nearly
     one inch at Tillamook.  The southern Willamette Valley
     picked up from one-tenth to one-quarter of an inch, while
     the north valley generally received between one-quarter and
     one-half inch.

     Snow levels dropped to about 5000 feet, in the Cascades, by
     early this morning.  Three inches of new snow fell overnight
     at Timberline Lodge.  ODOT cameras snowed a rain/snow mix
     over the Cascade passes, at mid-morning, with generally just
     wet pavement.  The storm was strong enough to spread some
     light rain across the northern half of central and eastern
     Oregon.  Most areas picked up a few hundredths of an inch,
     with up to one-quater inch falling in the Pendleton area.

     The front also greatly improved ventilation conditions by
     cooling the air aloft and eliminating the persistently
     strong low-level temperature inversion over western Oregon. 
     The Salem sounding this morning showed considerable cooling
     aloft.  3000-foot temperatures had cooled from nearly 60
     degrees, Monday morning, to about 40 degrees.  That should
     help mixing heights climb above 2000 feet this afternoon. 
     Transport winds winds were south-southwesterly, at about 15
     mph, with the flow aloft veering to northwesterly in
     response to a building ridge of high pressure.

     High pressure will build back over the region today with
     clearing skies across the state.  Doppler radar showed a few
     showers in the northern Cascades and near the Idaho border,
     but those should taper off by this afternoon.  Even with
     some sunshine temperatures will likely be a couple of
     degrees cooler today, due to the much colder air aloft. 
     Valley highs should top out around 55 degrees with continued
     south-southwesterly winds making for good ventilation conditions.

Surface Winds:
     SW 5-15 this morning, SW 5-12 this afternoon.
Transport Winds:
     SSW 15 this morning, SW 12 this afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height today will be near 2200 feet.  Ventilation index 33.
High Temperature:
     Salem\'s high temperature today will be near 55.
Humidities:
     Minimum relative humidity will be near 80%.
Sunrise/Sunset:
     Salem sunset tonight: 4:32pm; sunrise tomorrow: 7:33am.

Extended Outlook:
     The upper-level ridge will continue to build over the region
     Wednesday and will likely last into the weekend.  warming
     aloft will result in deteriorating ventilation conditions,
     with areas of valley fog reforming tonight.  The fog and low
     clouds will be slow to clear, Wednesday and Thursday
     afternoon, especially in the central and southern valley. 
     Increasing offshore flow will help generate enough easterly
     outflow, from the Colubia Gorge, to keep widespread fog out
     of the extreme north valley by Thursday.  The offshore flow
     is forecast to decrease Friday with increasing fog and low
     clouds in the north valley.

     The ridge of high pressure is forecast to remain over the
     region into Saturday.  Some flattening of the ridge may
     begin late Saturday with a chance of light rain in the north
     valley.  There is considerable disagreement in the
     long-range models regarding how and when the ridge will
     break-down beginning next week.  A major change in the
     weather pattern is likely after this weekend, but exactly
     what form that will take remains to be seen.  Increased
     onshore flow may combine with lowering snow levels to
     finally bring some significant snow to the mountains.

Tomorrow (03 Dec):  Morning Low Clouds and Fog.  Partial Afternoon Clearing.  37/50

Thu (04 Dec):  Morning Low Clouds and Fog.  Partial Afternoon Clearing.  34/50

Fri (05 Dec):  Morning Low Clouds and Fog.  Partial Afternoon Clearing.  34/49

Sat (06 Dec):  Areas of AM Fog.  Mostly Cloudy.  Slight Chance of Sprinkles North.  36/50

Sun (07 Dec):  Chance of Showers.  39/50

Mon (08 Dec):  Chance of Light Rain...Mainly North.  39/52

Tue (09 Dec):  Rain Likely.  Snow Level Dropping to 4000 feet.  38/49

ODA Meteorologist
weather at oda.state.or.us