[willamette-fcst] Forecast - Wednesday, May 6th, 2009

Wed May 6 09:09:10 PDT 2009

Daily Smoke Management Forecast

Oregon Department of Agriculture
Smoke Management Program
Weather Outlook and Field Burning Advisory for Willamette Valley Growers and Fire Districts.

...Corrected Extended Forecast for Sunday, May 10th...

Issued: 
     Wednesday, May 6th, 2009 at 9:00am.

Burn Advisory:
     Agricultural burning is allowed.  Suggested burn times are from now until 6:30pm.
     Straw stack burning is allowed, for dry stacks, from now until 6:30pm.

Weather Discussion:
     The Pacific Northwest remains under the influence of a
     strong and moist westerly flow aloft.  Showers briefly
     decreased Tuesday afternoon across western Oregon, but
     clouds increased again Tuesday night with rain spreading
     inland overnight.  Steady light to moderate rain was falling
     along the coast and across the Willamette Valley at
     mid-morning, ahead of a cold front, about 150 miles
     offshore.  Southerly winds were gusting to about 30 mph from
     Astoria to Newport.  South-southeasterly winds had increased
     in the Willamette Valley to between 10 and 15 mph.

     Clouds, rain, and wind made for mild overnight temperatures
     across western Oregon.  Minimums were near 50 degrees with
     mid-morning temperatures in the low 50s.  The Salem sounding
     from early this morning showed a similar temperature profile
     to Tuesday morning with the freezing level at 5600 feet. 
     South-southwesterly winds, grater than 30 mph, extended down
     to about 2000 feet.  Relative high mixing heights and brisk
     transport winds will make for good ventilation condtions
     today.  However, conditions may be too damp for stack burning.

     The mid-morning ODA surface analysis showed
     south-southeasterly gradients increasing across the
     Willamette Valley, in response to the approaching cold
     front.  Light southerly gradients east of the Cascades were
     also beginning to increase.  Satellite imagery showed clouds
     covering virtually all of Washington, Oregon, and Idaho. 
     Doppler radar showed areas of rain across all of Oregon with
     a zone of moderate rain extending from the northern and
     central coast range into the central and southern Willamette
     Valley.  Surface reports indicated occasional moderate to
     heavy rain along the coast with light to moderate rain in
     the Willamette Valley.

     More than one-half inch of rain has fallen from Astoria to
     Newport since late last night.  Only a few hundredths of an
     inch have fallen along the south coast and across
     southwestern Oregon.  In the Willamette Valley, the Portland
     and Salem airports have received about one-quarter of an
     inch of rainfall in the past 6 hours, with .15 inches
     falling in Eugene.  Rain was also falling over the Cascade
     passes at mid-morning, where temperatures were holding in
     the mid to upper 30s.  Areas of light rain extended east of
     the Cascades into Idaho.

     Steady rain should turn more showery across western Oregon
     this afternoon, as the cold front comes onshore and
     eventually pushes east of the Cascades.  Surface winds will
     veer to south-southwesterly, and may become a bit blustery,
     in the Willamette Valley this afternoon.  Cloudy skies and
     occasional showers will hold high temperatures in the upper
     50s again today.

Surface Winds:
     SSE 10-15 G20 this morning, SSW 10-20 G25 this afternoon.
Transport Winds:
     SSW 30 this morning, SW 30 this afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height today will be near 3300 feet.  Ventilation index 99.
High Temperature:
     Salem\'s high temperature today will be near 59.
Humidities:
     Minimum relative humidity will be near 72%.
Sunrise/Sunset:
     Salem sunset tonight: 8:24pm; sunrise tomorrow: 5:53am.

Extended Outlook:
     A continued strong onshore flow and a cool upper-level
     trough will maintain shower activity over western Oregon
     through Thursday morning, with some showers possibly
     lingering into Thursday afternoon, especially over the
     northern Cascades.  The snow level will drop to about 4000
     feet Thursday with some wet snow possible over the Cascade passes.  

     A drier northwesterly flow aloft will take over Friday and
     Saturday with temperatures warming to slightly above average
     by Saturday.  The ridge is forecast to push east of the
     region Sunday with the flow aloft turning westerly again.  A
     weak weather system may bring back some showers by Sunday
     evening.  A developing 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.

Thu (07 May):  Scattered Showers, Decreasing in the Afternoon.  Snow Level 4000 Feet.  46/58

Fri (08 May):  Mostly Cloudy AM.  Partly Cloudy PM.  39/64

Sat (09 May):  Partly Cloudy.  40/68

Sun (10 May):  Increasing Clouds.  Chance of Showers Late.  42/69

Mon (11 May):  Increasing Chance of Showers and Cooler.  45/60

Tue (12 May):  Showers Likely.  Snow Level 4000 Feet.  44/59

Wed (13 May):  Showers Likely.  Snow Level 3-4000 Feet.  43/58

ODA Meteorologist
weather at oda.state.or.us