[willamette-fcst] Forecast - Thursday, March 26th, 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.

NOON UPDATE

...Next update scheduled for Monday, March 30th, 2009 at 9:00am...

Issued: 
     Thursday, March 26th, 2009 at 12:00pm.

Burn Advisory:
     Agricultural burning is allowed.  Suggested burn times are from now until 5:30pm.
     Straw stack burning is allowed from now until 5:30pm.

Weather Discussion:
     Skies cleared overnight across western Oregon, as an
     upper-level disturbance slid southeastward into Idaho and
     Utah.  That allowed temperatures to drop into the 30s with
     some areas dipping below freezing.  Hillsboro was one of the
     coldest spots with a minimum of 28 degrees.  Aurora fell to
     33.  McMinnville and Salem bottomed out at 34.  Corvallis
     recorded a minimum of 37 degrees, followed closely by Eugene
     at 38.  Clearing skies also allowed temperatures to dip
     close to the freezing mark along the north coast.  Astoria
     dropped down to 34 degrees.  Slowly clearing skies helped
     temperatures east of the Cascades drop into the teens and
     20s.  With a fresh snow-cover, Meacham, in the Blue Mountains
     of northeastern Oregon, was the cold spot in the state with
     a minimum of just 14 degrees.

     Late-morning satellite imagery showed middle and high clouds
     covering the western half of both Washington and Oregon, in
     advance of a weak warm front about 200 miles offshore. 
     Skies were mostly sunny east of the Cascades, except for
     areas of low clouds in some higher valley spots like
     La Grande.

     The late-morning ODA surface analysis continued to show high
     pressure centered over eastern Washington and low-pressure over
     northern California.  That was producing very weak northerly
     gradients across western Oregon and stronger northwesterly
     gradients east of the Cascades.  Willamette Valley winds had
     backed from northeasterly to northerly at around 5 mph.  Brisk
     northwesterly winds were gusting over 30 mph across the eastern
     third of the state.  Temperatures were in the mid 40s to low 50s
     across western Oregon, with 30s and 40s east of the Cascades.

     The Salem sounding this morning showed a pretty cold air
     mass over the region with the freezing level at just 3000
     feet.  Middle and high clouds will continue to increase
     across western Oregon today, as the offshore warm front
     slowly moves northeastward towards the Washington Coast. 
     The freezing level should lift to near 6000 feet by late
     this afternoon.  Warmer air aloft will act to suppress
     mixing heights and convection this afternoon, so generally
     dry and mild conditions will prevail.

     Doppler radar was showing possible areas of sprinkles or light
     rain moving onto the central Oregon Coast and into the coastal
     range, so some afternoon sprinkles are not out of the question.
     Valley temperatures should warm into the mid to upper 50s, even
     with the increased cloud-cover.  Transport winds will remain fairly
     light and turn slightly more westerly by late this afternoon.
     As the warm front moves onshore tonight, there is a better
     chance of sprinkles or light rain...mainly along the coast.
     Cloudy skies should keep overnight temperatures near 40 degrees
     across the Willamette Valley with light winds. 

Surface Winds:
     NW 5 this afternoon.
Transport Winds:
     NNW 5 this afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height today will be near 2400 feet.  Ventilation index 19.
High Temperature:
     Salem\'s high temperature today will be near 57.
Humidities:
     Relative humidity drops to 50% by 2pm.
     Minimum relative humidity will be near 47%.
Sunrise/Sunset:
     Salem sunset tonight: 7:33pm; sunrise tomorrow: 7:02am.

Extended Outlook:
     The jet stream is forecast to migrate slightly northward
     Friday, with skies staying mostly cloudy across Washington
     and extreme northern Oregon.  Some sprinkles are possible
     near the Washington border, and along the coast, with a few
     sunbreaks in the Willamette Valley.  The snow level will
     remain around 5000 over northern Oregon and to 6-7000 feet
     over southern Oregon.  Willamette Valley temperatures should
     be slightly above normal.

     A vigorous cold front is forecast to swing onshore Saturday
     afternoon and night, with more rain, wind, and rapidly
     lowering snow levels.  Showers will taper off Sunday, as a
     transitory upper-level ridge moves over the region.  Another
     cold front is forecast to sweep across Washington and
     northern Oregon Monday with some drying Tuesday.  More
     storms are forecast to swing across southern British
     Columbia Wednesday through Friday but may extend far enough
     south to bring some rain to mainly northern Oregon.

Fri (27 Mar):  Chance of Sprinkles...Mainly North.  Mild.  Snow Level 5-7000 Feet.  40/61

Sat (28 Mar):  PM Rain & Blustery. Snow Level 4500 Feet...Dropping Late.  42/54

Sun (29 Mar):  Showers Ending...PM Clearing. Snow Level Lifting to 3500 Feet Late.  36/52

Mon (30 Mar):  Increasing Chance of Rain...Mainly North.  Snow Level 3500 Feet.  37/54

Tue (31 Mar):  Chance of Showers.  Snow Level 3000 feet.  37/53

Wed (01 Apr):  Mostly Cloudy.  Chance of Rain.  37/56

Thu (02 Apr):  Mostly Cloudy.  Slight Chance of Rain...Mainly North.  37/58

ODA Meteorologist
weather at oda.state.or.us