[willamette-fcst] Forecast - Friday, May 8th, 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, May 8th, 2009 at 9:00am.

Burn Advisory:
     Agricultural burning is allowed.  Suggested burn times are from now until 6:30pm.
     Stack burning is not allowed.

Weather Discussion:
     A continued strong onshore flow and a cool upper-level
     trough, cutting across Washington and northern Oregon,
     maintained shower activity across western Washington and the
     northern half or Oregon through much of Thursday.  Some of
     the showers produced brief bursts of moderate to heavy rain
     and small hail, especially from about Salem northward.  Most
     of the Willamette valley received less than one-tenth of an
     inch of rain, due to the rain-shadow effect from westerly
     flow aloft downsloping off the coast range.  Measurable rain
     extended as far south as Sexton Summit, between Roseburg and Medford.

     Snow levels stayed near 3500 feet over the northern Cascades
     Thursday, as upsloping westerly flow aloft produced
     frequent, and at times quite potent, showers.  Timberline
     Lodge received 8 inches of new snow in the past 24 hours and
     20 inches in the past 72 hours.  They still had a base snow
     total of 201 inches this morning!  Showers had finally
     ended, with clearing skies, over the Cascades this morning. 
     Warmer air aloft was making it northward across Oregon this
     morning.  The freezing level over Salem was measured at just
     3900 feet early this morning, but the freezing level over Medford
     had jumped to 7900 feet.  The freezing level over northern Oregon
     should rise to around 7000 feet by late this afternoon.

     Clearing skies and decreasing winds allowed western Oregon
     temperatures to locally drop into the mid 30s overnight. 
     Hillsboro dipped to 34 degrees and Eugene fell to 35. 
     McMinnville and Salem both dropped to 37 degrees.  On the
     coast, Newport also fell to 37 degrees, before fog formed
     and stabilized the temperature.  There was enough ground
     moisture available for patchy fog to develop both on the
     coast and in the Willamette Valley early this morning. 
     There were also pockets of marine low clouds.  Clearing
     skies helped temperatures locally drop as low as the mid 20s
     across eastern Oregon.  Baker City was the cold spot in the
     state this morning with a minumum of 25 degrees.

     A drier northwesterly flow aloft covers the region this
     morning.  Visible satellite imagery showed mostly cloudy
     skies across western Washinton with areas of low clouds
     extending southward across the northern Oregon Coast.  Areas
     of low clouds also covered pockets in the western valleys of
     Oregon.  Skies were mostly sunny across the remainder of
     Oregon and over central and eastern Washington.  Mid-morning
     temperatures has already warmed well into the 40s across all
     of western Oregon with readings in the upper 30s and 40s
     east of the Cascades.

     The ODA surface analysis showed a thermal trough over
     northern California beginning to build northward into
     southwestern Oregon.  Weak northerly gradients will increase
     across western Oregon later today with north winds becoming
     brisk along the coast.  Northerly winds will also increase
     in the Willamette Valley, especially in the south valley
     near Eugene.  Warming aloft and mostly sunny skies will help
     temperatures recover to near normal this afternoon.  Mostly
     clear skies tonight will allow temperatures to locally drop
     into the mid to upper 30s across western Oregon again
     tonight.  Patchy fog may form early Saturday morning.

Surface Winds:
     N 5-10 this morning, N 5-15 G20 South this afternoon.
Transport Winds:
     NNE 15 this morning, N 15 this afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height today will be near 4600 feet.  Ventilation index 69.
High Temperature:
     Salem\'s high temperature today will be near 64.
Humidities:
     Minimum relative humidity will be near 40%.
Sunrise/Sunset:
     Salem sunset tonight: 8:26pm; sunrise tomorrow: 5:50am.

Extended Outlook:
     A dry northwesterly flow aloft will continue Saturday with
     mostly sunny skies warming temperatures slightly above
     average.  The upper-level ridge is forecast to push east of
     the region Sunday with the flow aloft turning westerly
     again.  Temperatures will stay above average Sunday, but
     clouds will be on the increase.  Light rain may return as
     early as Sunday evening.

     A strengthening upper-level trough is forecast to drop over
     the region during the first half of next week, bringing a
     return of cool and damp weather.  Snow levels will drop to
     near or below the Cascade passes.  There is considerable
     disagreement in the long-range computer models for the
     second half of next week.  It appears that another weather
     system may move onshore Wednesday and Thursday.

Tomorrow (09 May):  Mostly Sunny with Seasonal Temperatures.  38/68

Sun (10 May):  Increasing Clouds.  Chance of Rain Late.  41/70

Mon (11 May):  Rain Likely and Cooler.  Snow Level Dropping to 4000 Feet Late.  46/59

Tue (12 May):  Showers Likely...Mainly North.  Snow Level 4000 Feet.  43/59

Wed (13 May):  Mostly Cloudy.  Chance of Rain... Mainly North.  Snow Level 5000 Feet.  43/62

Thu (14 May):  Mostly Cloudy.  Chance of Rain.  Snow Level 6000 Feet.  46/65

Fri (15 May):  Chance of Showers.  Snow Level 6-7000 Feet.  47/67

ODA Meteorologist
weather at oda.state.or.us