[willamette-fcst] Forecast - Friday, February 6th, 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: 
     Friday, February 6th, 2009 at 9:00am.

Burn Advisory:
     Agricultural burning is allowed.  Suggested burn times are from now until 3:30pm.
     Stack burning is not allowed.

Weather Discussion:
     The massive upper-level ridge of high pressure, that brought
     stagnant weather conditions to the Pacific Northwest for
     most of January, is finally breaking down.  A weather
     system, dropping southeastward from the Gulf of Alaska,
     helped to kick inland an upper-level low pressure system,
     off the California coast.  The combination of systems
     brought cloudy skies to the region Thursday with light
     spreading across western Oregon Thursday evening.

     The morning sounding over Salem showed a deep layer of
     significant cooling, since Thursday morning.  There was
     still a weak low-level temperature inversion, from the
     surface up to about 1500 feet, but ventilation conditions
     have dramatically improved over the region. freezing level
     had dropped from 8900 feet Thursday morning to only 4800
     feet this morning.  ODOT road cameras showed snow beginning
     to fall over the Cascade passes this morning with pass
     temperatures near freezing.  In contrast, clouds and rain
     kept valley temperatures warmer overnight, where minimums
     were near 40 degrees.  The ODA surface analysis showed very
     weak pressure gradients across Oregon and Willamette Valley
     winds were were light at mid-morning.

     Rainfall amounts in the past 24 hours range from about
     one-tenth to one-third of an inch across western Oregon. 
     The weak upper-level trough over the region is forecast to
     push far enogh east by this afternoon for the flow aloft to
     become northerly and begin drying out.  Showers will
     decrease across western Oregon this afternoon and evening. 
     The snow level should drop to about 3000-3500 feet with
     several inches of snow possible over the Cascade passes. 
     Valley temperature will be cooler this afternoon with highs
     in the mid to upper 40s.  High pressure will begin building
     into the coastline with surface winds becoming
     north-northwesterly.  Partial clearing overnight should
     promote fog formation across much of western Oregon with
     temperatures dropping into the mid 30s.

Surface Winds:
     N 0-5 this morning, NNW 5-10 this afternoon.
Transport Winds:
     N 3 this morning, N 9 this afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height today will be near 1900 feet.  Ventilation index 17.
High Temperature:
     Salem\'s high temperature today will be near 47.
Humidities:
     Minimum relative humidity will be near 76%.
Sunrise/Sunset:
     Salem sunset tonight: 5:28pm; sunrise tomorrow: 7:24am.

Extended Outlook:
     A transitory ridge will likely bring a dry and farily mild
     day to the region Saturday.  Another weather system is
     forecast to bring more rain and mountain snow Sunday
     afternoon and night with the snow level dropping to 3000
     feet.  Showers will continue Monday with very low snow
     levels.  There may be a brief break early Tuesday, ahead of
     the next cool weather system.  More cool weather systems are
     forecast to sweep across the region later in the week.

Sat (07 Feb):  Areas AM Fog.  Partly Cloudy and Mild.  Freezing Level 5-6000 Feet.  34/51

Sun (08 Feb):  Increasing Clouds.  Rain Developing PM.  Snow Level 3-4000 feet.  32/46

Mon (09 Feb):  Showers...Decreasing Late.  Snow Level 1500 Feet.  34/45

Tue (10 Feb):  Areas AM Fog.  Rain Developing in the Afternoon.  Snow Level 2000 Feet.  32/45

Wed (11 Feb):  Showers...Decreasing Late.  Snow Level 1500 Feet.  34/45

Thu (12 Feb):  Mostly Cloudy.  Increasing Chance of Rain Late.  34/47

Fri (13 Feb):  Rain with Mountain Snow.  Snow Level 1000 Feet.  34/45

ODA Meteorologist
weather at oda.state.or.us