[willamette-fcst] Forecast - Wednesday, November 26th, 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: 
     Wednesday, November 26th, 2008 at 9:00am.

Burn Advisory:
     Agricultural burning is not recommended.
     Stack burning is not allowed.

Weather Discussion:
     A weak cold front managed to lift the dense fog from the
     Willamette Valley Tuesday but replaced it with a low
     overcast and light rain.  Valley temperatures were chilly
     with highs only climbing into the low to mid 40s.  Rainfall
     totals ranged from just a few hundredths of an inch, in the
     south valley, up to one-quarter of an inch in sections of
     the north valley.  Only light precipitation fell in the
     Cascades, where the snow level stayed above about 6000 feet.

     The morning ODA surface analysis showed the cold front had
     moved east of the region and stretched from western Montana
     to the northeastern tip of Oregon.  A stronger low pressure
     area was bringing rain to central and southern California. 
     Dry conditions prevailed across Oregon with northerly
     surface gradients.  There was some middle and high
     cloudiness circulating northward, over Oregon, from the
     California weather system.  Visible satellite imagery showed
     considerable low clouds and areas of fog in the valleys of
     western and north-central Oregon.

     The Salem sounding this morning showed some cooling aloft
     since Tuesday, but not enough to break the low-level
     temperature inversion over the region.  Mixing heights will
     be a little higher today than on Tuesday, but ventilation
     remains poor over the valley.  Surface and transport winds
     were north-northeasterly.  Northerly winds increased to
     about 10 mph acros most of the valley this morning, which
     kept temperatures from falling below the upper 30s.  Light
     winds did allow hillsboro to drop to 31 degrees.

     A transitory ridge is forecast to maintain dry conditions
     today, although fog may be persistent...especially in the
     central and southern Willamette Valley.  Increasing offshore
     flow will help the fog and low clouds clear from the north
     valley, with some afternoon sunshine.  Valley highs should
     climb mostly into the low 50s, which is above normal for
     late November.  Winds wind continue to increase slightly and
     turn more northeasterly this afternoon.

Surface Winds:
     N 10 this morning, NE 10-15 this afternoon.
Transport Winds:
     N 12 this morning, NE 14 this afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height today will be near 2000 feet.  Ventilation index 28.
High Temperature:
     Salem\'s high temperature today will be near 52.
Humidities:
     Minimum relative humidity will be near 59%.
Sunrise/Sunset:
     Salem sunset tonight: 4:34pm; sunrise tomorrow: 7:26am.

Extended Outlook:
     A splitting weather system will possibly be strong enough to
     bring a little rain to western Oregon late Thanksgiving day.
     A warm front will brush the northwest corner of Oregon with
     some clouds and a slight chance of light rain Friday.  A
     strong upper-level ridge is forecast to rebuild over the
     region, beginning Friday night, with a continuation of
     stagnant weather conditions and areas of persistent valley fog.  

     Increasing offshore flow will act to keep widespread fog out
     of the north valley Saturday and Sunday, but fog could
     become widespread and persistent in the central and southern
     valley.  A weather system may flatten the ridge and bring a
     chance of rain as early as Monday of next week, but that is
     getting beyond the range of the computer models forecasts
     with this weather pattern.

Tomorrow (27 Nov):  Areas of AM Fog.  Increasing Chance of Light Rain Late.  34/50

Fri (28 Nov):  Areas of Fog.  Mostly Cloudy.  37/49

Sat (29 Nov):  Areas of Fog.  Partly Sunny in the Afternoon...Mainly North.  33/51

Sun (30 Nov):  Areas of Fog.  Partly Sunny in the Afternoon...Mainly North.  33/51

Mon (01 Dec):  Increasing Chance of Light Rain.  35/52

Tue (02 Dec):  Areas of Fog.  Partly Sunny...Mainly North.  33/49

Wed (03 Dec):  Areas of Fog.  Partly Sunny...Mainly North.  33/49

ODA Meteorologist
weather at oda.state.or.us