[willamette-fcst] Forecast - Thursday, February 11th, 2010

[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, February 11th, 2010 at 9:00am.

Burn Advisory:
     Recommended burn times for agricultural burning are from now to 3:30pm.
     Straw stack burning is allowed from now until 3:30pm.

Weather Discussion:
     ...The rules for stack burning have changed.  Stack burning permits must
     be obtained from ODA Smoke Management Personnel...

     A weakening frontal system spread mostly light rain across
     western Oregon Wednesday, before stalling over the region. 
     Increasing southerly winds, ahead of an approaching warm
     front, led to midnight maximum temperatures across much of
     western Oregon Wednesday night.  Willamette Valley readings
     climbed into the upper 40s by midnight, with some areas
     continuing to warm into the low 50s early this morning. 

     Satellite imagery showed a rather complex-looking cloud
     pattern extending from over Washington and Oregon to more
     than 400 miles offshore.  The fairly moist Pacific storm
     system was beginning to split apart, under the split-flow
     jet stream pattern just off the west coast.  A surface low
     pressure center appeared to be developing about 450 miles
     off the southern Oregon/northern California coastline, with
     a warm front advancing out ahead of it towards Washington
     and Oregon.

     Skies were cloudy across all of Oregon with Doppler radar
     showing areas of light rain and higher elevation snow
     sweeping from west to east across the state.  Between
     one-half and three-quarters of an inch of rain have fallen
     along the coast in the past 24 hours.  In contrast, inland
     precipitation amounts have been mostly light.  Western
     valleys have only received about one-tenth to one-quarter of
     an inch, with areas east of the Cascades generally picking
     up less than one-tenth of an inch.  Snow levels are on the
     rise and had climbed just above the Cascade passes by mid-morning.

     The offshore low pressure system is forecast to track close
     enough to the coastline later today to bring strong
     southerly winds to much of the Oregon Coast.  The National
     Weather Service has issued high wind warnings for the Oregon
     Coast, for southerly gusts up to 70 mph, late this afternoon
     through this evening.  Southerly winds will also increase
     today in the Willamette Valley, with gusts of 35-40 mph
     possible by this evening.  Rain will also be on the increase
     today, with snow levels likely staying above the passes.  It
     will be very mild, with southerly winds helping lift
     temperatures into the mid 50s. 

Surface Winds:
     SSE 10-20 G25 this morning, SSE 12-25 G35 Late this afternoon.
Transport Winds:
     S 25 this morning, S 35 this afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height today will be near 2500 feet.  Ventilation index 88.
High Temperature:
     Salem\'s high temperature today will be near 55.
Humidities:
     Minimum relative humidity will be near 69%.
Sunrise/Sunset:
     Salem sunset tonight: 5:35pm; sunrise tomorrow: 7:17am.

Extended Outlook:
     The cold front asociated with the offshore weather system
     will finally come onshore overnight...dropping the snow
     level to the Cascade passes.  3-6 inches of snow are
     possible, at pass level, before the precipitation tapers off
     Friday morning.  The brisk southerly winds across western
     Oregon will rapidly taper off overnight, in the wake of the
     frontal passage, with the steady rain turning showery and
     decreasing.

     A colder weather system is forecast to spread more rain
     onshore around midday Friday. The snow level will likely
     stay near or slightly below the Cascade passes. 
     Southeasterly winds will not be as brisk with this system
     but should provide good ventilation conditions.

     A transitory ridge of high pressure should dry things out
     Saturday, especially south, as a warm front brushes by to
     our north.  Afternoon temperatures could become quite mild
     Saturday with some sunbreaks possible.  A weak cold front
     will likely bring some light rain Sunday, with snow levels
     likely remaining above the Cascade passes.  Another warm
     front will bring a chance of rain Monday, with a weak cold
     front coming onshore Tuesday.  Next Wednesday and Thursday
     look dry & very mild, with increasing offshore flow, as a strong
     upper level ridge of high pressure builds over the west coast.

Fri (12 Feb):  Increasing Rain in the Afternoon.  Snow Level Dropping to 4000 Feet.  46/54

Sat (13 Feb):  Chance of Light North.  Mostly Cloudy South.  Snow Level 6000 Feet.  44/58

Sun (14 Feb):  Mostly Cloudy and Mild.  Chance of Light Rain.  Snow Level 5500 Feet.  41/53

Mon (15 Feb):  Chance of Light Rain...Mainly North.  Snow Level 6000 Feet.  39/54

Tue (16 Feb):  Chance of Rain.  Snow Level 5000 Feet.  37/54

Wed (17 Feb):  Areas of AM Fog.  Becoming Partly Sunny & Mild in the Afternoon.  36/57

Thu (18 Feb):  Mostly Sunny and Spring-Like.  38/62

ODA Meteorologist
weather at oda.state.or.us