[willamette-fcst] Forecast - Friday, February 5th, 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: 
     Friday, February 5th, 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.

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

Weather Discussion:
     A weakening frontal system dropped from about one-tenth to
     one-third of an inch of rain across western Oregon
     overnight.  Between a few hundredths and one-quarter of an
     inch of water-equivalent precipitation fell across central
     and eastern Oregon.  Snow levels were between 4000 and 5000
     feet overnight, so areas east of the Cascades saw a mix of
     rain and snow.  A few inches of new snow fell in the higher
     elevations of the Cascades.

     The main cloud-shield from this weather system was pushing
     into Idaho at mid-morning, with mostly cloudy skies
     remaining across Oregon.  Some rain and snow showers were
     still falling over mainly northeastern Oregon, with Doppler
     radar also showing some light rain showers over northwestern
     Oregon.  It was very mild overnight, west of the Cascades,
     where temperatures stayed mostly in the mid and upper 40s. 
     Temperatures east of the Cascades varied with elevation. 
     Higher locations stayed near freezing with occasional light
     snow, while the lower elevations stayed above freezing with
     occasional light rain.

     A southwesterly split-flow jet stream pattern, forced by a
     strong El Nino event in the tropical Pacific Ocean, will
     continue the mild early February weather across western
     Oregon.  The ODA surface analysis showed offshore pressure
     gradients across western Oregon with southeasterly winds in
     the 5-15 mph range.  Infrared satellite imagery showed some
     middle and high clouds circulating across northwestern
     Oregon this morning, but the next organized weather system
     was still about 200 miles off the northern California coast.
     residual low clouds this morning should yield to some sunbreaks
     today across western Oregon.  The air aloft is warm enough to
     support temperatures climbing into the mid 50s this afternoon,
     if we get enough mixing of the air mass...which is likely.

Surface Winds:
     SE 5-12 this morning, SE 5-15 this afternoon.
Transport Winds:
     S 15 this morning, S 18 this afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height today will be near 2500 feet.  Ventilation index 45.
High Temperature:
     Salem\'s high temperature today will be near 56.
Humidities:
     Minimum relative humidity will be near 59%.
Sunrise/Sunset:
     Salem sunset tonight: 5:26pm; sunrise tomorrow: 7:25am.

Extended Outlook:
     The next weather system is forecast to split apart, with the
     bulk of the moisture moving south, into California, on
     Saturday.  However, western Oregon will get plenty of clouds
     and at least some light rain...mainly south.  Weak
     southwesterly flow aloft will maintain fairly high snow
     levels, for early February, and mild surface temperatures.

     A transitory ridge of high pressure will bring drying to
     western Oregon Sunday, with continued very mild
     temperatures.  Snow levels will remain near the Cascade
     passes.  The next system is forecast to come onshore Monday.
     It will also weaken, as it encounters the split-flow jet
     stream pattern over Oregon but should be strong enough to
     spread some light rain and snow back across the state.  Snow
     levels are forecast to drop a little lower with this system,
     with accumulation snow over the Cascades passes
     likely...mainly south.

     Another transitory ridge is forecast to move onshore late
     Tuesday and Wednesday with precipitation tapering off across
     western Oregon.  Stronger weather systems are forecast to
     come onshore next Thursday and Friday, which could bring
     high coastal winds, along with more rain and mountain snow
     to western Oregon.

Sat (06 Feb):  Rain Likely South.  Chance of Rain North.  Snow Level 4000 Feet.  37/52

Sun (07 Feb):  Showers Ending with Some Sunbreaks.  Mild.  Snow Level 4000 Feet.  37/54

Mon (08 Feb):  Light Rain and Mountain Snow Likely.  Snow Level 3-4000 Feet.  36/50

Tue (09 Feb):  Mostly Cloudy.  Decreasing Chance of Showers.  Snow Level 3-4000 Feet.  39/52

Wed (10 Feb):  Patchy AM Fog.  Partly Sunny. Increasing Clouds in the Afternoon.  34/50

Thu (11 Feb):  Rain Likely...Possibly Windy Coast.  Snow Level 5000 Feet.  40/53

Fri (12 Feb):  Rain Likely...Possibly Windy Coast.  Snow Level 4-5000 Feet.  40/51

ODA Meteorologist
weather at oda.state.or.us