[willamette-fcst] Forecast - Wednesday, January 9th, 2008

Wed Jan 9 16:44:37 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.

Issued: 
     Wednesday, January 9, 2008 at 4:45 pm

Burn Advisory For Thursday, January 10, 2008:
     Agricultural burning is allowed.  Suggested burn times are from 8:00am until 3:00pm.
     Straw stack burning is allowed from 8:00am until 3:00pm.

Weather Discussion:
     A strong warm front spread light rain onto the Oregon Coast
     at midday and into the Willamette Valley this afternoon. 
     Satellite imagery showed a broad area of clouds extending
     from the coastline westward to the cold front, about 300
     miles offshore.  The late-afternoon ODA surface analysis
     showed southeasterly pressure gradients beginning to
     increase along the coast and in the Willamette Valley. 
     Winds were blowing about 10-15 mph across much of Western
     Oregon with temperatures in the low 40s.

     Southerly winds will increase along the coastline this
     evening, where high wind warnings are in effect for the
     northern and central coast, starting at 8 pm, for gusts to
     65 mph. It will turn rainy and blustery this evening in the
     Willamette Valley with south winds likely gusting to near 30
     mph tonight.  The valley should pick up about one-half inch
     of rain by Thursday morning.

     Warmer air is pushing northward across the state with the
     freezing level over Salem this afternoon measured at 3000
     feet and 4500 feet over Medford.  The precipitation is
     falling as rain over the northern coast range passes this
     afternoon, where the snow level has lifted to about 2000
     feet.  Snow levels will stay low enough for the Northern
     Cascade passes to see more significant snow tonight through
     Friday morning.

     Warmer air aloft will push the snow level to about 4000 feet
     by Thursday morning.  Colder air behind the cold front will
     lower the snow level back to 3000 feet by Thursday night. 
     The National Weather Service has issued a heavy snow warning
     from 10 pm tonight until 4 am Friday.  The passes could pick
     up a foot of snow overnight and frequent snow showers may
     dump another foot or more of snow Thursday and Thursday night.

     The steady rain overnight will turn to showers across the
     Willamette Valley tomorrow.  Blustery southerly winds and
     high relatively high winter-time mixing heights will make
     for good ventilation conditions.  Temperatures will climb
     above normal with morning lows not dropping much below 40
     degrees and afternoon highs approaching 50.

Surface Winds:
     S 10-20 G30 Thursday morning, SSW 10-15 G25 Thursday afternoon.
Transport Winds:
     SW 25-30 Thursday morning, SW 25-30 Thursday afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height Thursday will be near 3000 feet.  Ventilation index 75.
High Temperature:
     Salem\'s high temperature Thursday will be near 49.
Humidities:
     Minimum relative humidity will be near 80%.
Sunrise/Sunset:
     Salem sunrise Thursday: 7:49 pm; sunset Thursday: 4:51 am.

Extended Outlook:
     Showers will taper off Friday as a transitory ridge of high
     pressure moves over the region.  The next weather system is
     expected to be much weaker, as it moves across Oergon
     Saturday with only a little rain and mountain snow likely. 
     Temperatures will remain above normal with snow levels
     staying up at 4000 feet.  Ventilation conditions are likely
     to stay good through Saturday.  A transitory ridge of high
     pressure is forecast to bring drier conditions on Sunday
     with deteriorating ventilation conditions.

     The long-range computer models are showing a ridge of high
     pressure just offshore with a weak weather system dropping
     down the British Columbia Coastline and into the region
     Monday.  A dry northerly flow is currently forecast for
     Tuesday through Thursday of next week, but my confidence in
     this forecast is low, because the long-range models have
     been flip-flopping around like a fresh-caught trout.

Thu (10 Jan):  Rain Turning to Showers.  40/49

Fri (11 Jan):  Decreasing Showers.  40/49

Sat (12 Jan):  Light Rain Likely Early...Partial Clearing Late.  37/49

Sun (13 Jan):  Partly Cloudy.  Areas of Fog.  35/47

Mon (14 Jan):  Rain Turning to Showers with Mountain Snow Above 5000 Feet.  35/47

Tue (15 Jan):  Partly Cloudy.  Areas of Fog.  30/42

Wed (16 Jan):  Mostly Sunny and Cool.  Areas of Fog.  28/42

Thu (17 Jan):  Mostly Sunny and Cool.  Areas of Fog...Mainly South Valley.  28/42

ODA Meteorologist
weather at oda.state.or.us