[willamette-fcst] Forecast - Wednesday, October 28th, 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: 
     Wednesday, October 28th, 2009 at 9:00am.

Burn Advisory:
     Agricultural burning is allowed.  Suggested burn times are from 10:00am until 4:00pm.
     Straw stack burning is allowed from 10:00am until 4:00pm.

Weather Discussion:
     After a very wet Monday, with about one inch of rain falling
     along the coast and one-half inch across the Willamette
     Valley, showers tapered off Tuesday, with Willamette Valley
     rainfall amounts ony around one-tenth of an inch or less. 
     The early-week weather system brought 6-12 inches of snow to
     the Cascade passes.  Conditions were dry this morning, but
     the passes remained snow-packed with temperatures in the mid
     20s.  The freezing level was measured over Salem this
     morning at only 3700 feet.

     Light winds and partial clearing allowed temperatures to
     drop well into the 30s across western Oregon overnight. 
     McMinnville dipped to the freezing mark and Hillsboro
     dropped to 34 degrees.  Residual cloudiness prevented
     widespread fog from forming across western Oregon overnight,
     but there were some patches of fog in the Willamette Valley
     this morning. Satellite imagery showed considerable middle
     and high clouds streaming over Washington and Oregon, in a
     cool but dry northwesterly flow aloft.

     The ODA surface analysis showed high pressure over western
     Oregon with very weak southerly gradients across the
     Willamette Valley.  Mid-morning temperatures ranged from the
     mid 30s to the low 40s, under mostly cloudy skies with light
     south-southeasterly winds.  Skies will remain mostly cloudy
     today, as a Pacific warm front slowly approaches the
     coastline.  Precipitation should remain offshore, however,
     until this evening.

     Cool surface temperatures and warming aloft will combine to
     keep mixing heights near or below about 2000 feet this
     afternoon, but wind directions are favorable for stack
     burning.  Southerly winds should increase overnight, in
     response to the approaching warm front, which will aid in
     the continued evacuation of smoke from stack burns.  Light
     rain should also spread inland overnight, which will keep
     temperatures in the 40s.

Surface Winds:
     SSE 3-6 this morning, SE 3-7 this afternoon.
Transport Winds:
     SSW 5 this morning, S 6 this afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height today will be near 2000 feet.  Ventilation index 12.
High Temperature:
     Salem\'s high temperature today will be near 52.
Humidities:
     Minimum relative humidity will be near 59%.
Sunrise/Sunset:
     Salem sunset tonight: 6:06pm; sunrise tomorrow: 7:47am.

Extended Outlook:
     A warm front will spread rain across most of western Oregon
     Thursday.  The Willamette Valley will likely receive between
     one-quarter and one-half inch of rain, with the greatest
     totals in the north.  Rapid warming aloft should lift the
     freezing level to nearly 10,000 feet by Thursday evening. 
     Surface temperatures will slowly rise, on Thursday, with
     warming southerly winds possibly leading to midnight
     maximums Thursday night.

     The steady rain will likely taper off by Friday morning with
     areas of fog forming.  Friday will be spent in the
     warm-sector of the storm, with afternoon clearing and
     southerly breezes likely warming temperatures into the low
     to mid 60s.  The cold front is forecast to bring rain
     onshore Friday night, with showers continuing into Saturday.

     The air mass behind this cold front is not nearly as cold
     as the one earlier this week, with the snow level only
     forecast to drop to about 6-7000 feet Saturday afternoon. 
     The showers will likely taper off just in time for the
     trick-or-treaters Saturday night.  A flat and broad ridge of
     high pressure is forecast to bring dry conditions early next week.

Tomorrow (29 Oct):  Rain.  Slowly Warming Temperatures.  South Winds 10-20 mph.  43/55

Fri (30 Oct):  Areas of AM Fog.  Partly Sunny and Mild.  South Winds.  52/63

Sat (31 Oct):  Rain Early...Decreasing Showers.  49/59

Sun (01 Nov):  Mostly Cloudy.  43/58

Mon (02 Nov):  Mostly Cloudy.  42/57

Tue (03 Nov):  Mostly Cloudy.  42/58

Wed (04 Nov):  Mostly Cloudy.  41/56

ODA Meteorologist
weather at oda.state.or.us