[willamette-fcst] Forecast - Thursday, April 9th, 2009

[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: 
     Thursday, April 9th, 2009 at 9:00am.

Burn Advisory:
     Agricultural burning is allowed.  Suggested burn times are from now until 6:00pm.
     Straw stack burning is allowed from now until 6:00pm.

Weather Discussion:
     The upper-level trough that brought a fair amount of rain to
     south-central Oregon Wednesday, had moved eastward into to
     Rockies by early this morning.  However, another, weakening,
     cold front pushed a new batch of clouds, along with areas of
     light rain and mountain snow, across the state overnight. 
     Rainfall amounts have been very light, with the offshore
     cold front weakening under a split-flow pattern in the jet
     stream.  Up to about one-tenth of an inch of rain has fallen
     across portions of western Oregon, with most areas seeing a
     few hundredths of an inch.

     The Salem sounding this morning showed a little more cooling
     aloft, since Wednesday, with the freezing level measured at
     just 4000 feet.  ODOT road reports indicated some snow
     showers over the Cascade passes, with the road cameras
     showing wet pavement.  Pass temperatures were near the
     freezing mark at mid-morning.

     The ODA surface analysis showed much weaker pressure
     gradients across the state compared with yesterday.  A weak
     trough, associated with a cold front, was just off the
     coast, resulting in south-southeasterly gradients across
     most of the state.  Winds were in the 5-15 mph range
     statewide.  Mid-morning temperatures were in the mid to
     upper 40s west of the Cascades, with readings in the 30s to
     mid 40s across central and eastern Oregon.

     A developing low-pressure center, along the southern portion
     of the cold front, will take most of the rain and snow from
     this system into northern California today.  However, as the
     weakening cold front moves onshore, a moist southwesterly
     flow aloft will keep skies mostly cloudy over Oregon with
     areas of very light rain and mountain snow continuing today.
     High temperatures will be similar to yesterday...several
     degrees below normal.

Surface Winds:
     SSE 5-15 this morning, SW 5-15 this afternoon.
Transport Winds:
     S 22 this morning, SW 17 this afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height today will be near 5000 feet.  Ventilation index 110.
High Temperature:
     Salem\'s high temperature today will be near 54.
Humidities:
     Minimum relative humidity will be near 68%.
Sunrise/Sunset:
     Salem sunset tonight: 7:50pm; sunrise tomorrow: 6:36am.

Extended Outlook:
     An upper-level trough will dive south of the region, into
     California, Friday.  That will put Oregon under a split-flow
     pattern with weak southwesterly flow aloft keeping skies
     mostly cloudy but with only a minimal threat of rain. 
     Temperatures will continue below normal.  The next weather
     system will move mainly north of Oregon Saturday, but the
     trailing cold front should keep skies mostly cloudy with at
     least a chance of a little rain...mainly north.

     The jet stream becomes more consolidated over the region
     with a stronger system slated to come onshore sometime on
     Easter Sunday.  The timing of that system has been the
     biggest question mark, but the lastest computer models are
     starting to agree on rain spreading across western Oregon
     Sunday afternoon and evening.  A very cold upper-level
     trough is forecast to drop over the region Monday, with the
     trough slowly pushing east Tuesday.  A transitory ridge is
     forecast to bring some drying and warming around the middle
     of next week, but westerly flow aloft should keep skies
     mostly cloudy.

Tomorrow (10 Apr):  Mostly Cloudy.  Chance of Light Showers.  Snow Level 4000 Feet.  41/56

Sat (11 Apr):  Mostly Cloudy.  Chance of Light Rain...Mainly North.  42/57

Sun (12 Apr):  Rain Developing by Afternoon.  Snow Level 5000 Feet.  44/57

Mon (13 Apr):  Showers with Mountain Snow.  Snow Level Dropping to 2500 feet.  41/52

Tue (14 Apr):  Decreasing Showers...Partial Clearing.  Snow Level 2500 Feet.  37/54

Wed (15 Apr):  Becoming Partly Sunny and Warmer.  35/59

Thu (16 Apr):  Mostly Cloudy.  39/60

ODA Meteorologist
weather at oda.state.or.us