[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.

Issued: 
     Thursday, March 26th, 2009 at 9:00am.

Burn Advisory:
     Agricultural burning is allowed.  Suggested burn times are from 11:00am until 5:30pm.
     Straw stack burning is allowed from 11:00am 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 29 degrees.  Aurora fell to
     34 and McMinnville bottomed out at 35.  Corvallis and Salem
     both recorded minimums of 37 degrees.  Clearing skies also
     allowed temperatures to dip close to the freezing mark along
     the north coast.  Astoria dropped down to 34 degrees. 
     Slowly clearing helped temperatures east of the Cascades fal
     mostly 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.

     Mid-morning satellite imagery showed middle and high clouds
     moving onto the Washington and northern Oregon coast, in
     response to an approaching warm front about 200 miles
     offshore.  Skies were mostly clear across Oregon, except for
     pockets of valley low clouds on both sides of the Cascades.
     The mid-morning ODA surface analysis showed high pressure
     centered over eastern Washington and a low-pressure center
     over northern California, west of Reno, Nevada.  That was
     producing very weak northerly gradients across western
     Oregon and a little stronger gradients east of the Cascades.
     Willamette Valley winds were generally north-northeasterly
     from 0-5 mph with temperatures in the 30s and low 40s.
     North-northwesterly winds were cutting across eastern Oregon,
     where temperatures were generally in the 20s and low 30s.

     The Salem soundinn this morning indicated some cooling and
     drying of the air mass, in the wake of the disturbance that
     moved through yesterday.  The freezing level was at just
     3000 feet.  Middle and high clouds will continue to increase
     across western Oregon today, as a weak warm front offshore
     slowly moves northeastward towarsd 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.  Valley
     temperatures should warm into the mid to upper 50s, even
     with the increased cloud-cover.  Transport winds will remain
     fairly light and turn more westerly by late this afternoon. 
     As the warm front moves onshore tonight, clouds will lower
     and thicken enough for a chance of sprinkles or light
     rain...mainly along the coast.

Surface Winds:
     NNE 0-5 this morning, NW 5 this afternoon.
Transport Winds:
     NE 8 this morning, 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.  A dissipating warm front should keep skies mostly
     cloudy across Washington and northern Oregon.  Some
     sprinkles are possible, along with a few sunbreaks.  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 for a change.

     A vigorous cold front is forecast to swing onshore late
     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 and Blustery. Snow Level 4500 Feet...Dropping Late.  42/54

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

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

Tue (31 Mar):  Showers and Cooler.  Snow Level 3000 feet.  37/52

Wed (01 Apr):  Mostly Cloudy.  Increasing Chance of Rain Late.  34/57

Thu (02 Apr):  Mostly Cloudy.  Chance of light Rain...Mainly North.  37/57

ODA Meteorologist
weather at oda.state.or.us