[willamette-fcst] Forecast - Friday, February 19th, 2010

[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

Issued: 
     Friday, February 19th, 2010 at 12:00pm.

Burn Advisory:
     Recommended burn times for agricultural burning are from now until 4:00pm.
     Stack burning is not allowed.

Weather Discussion:
     A strong upper-level ridge of high pressure, centered over
     northwestern British Columbia, is directing a dry
     north-northeasterly flow aloft across Oregon.  On the
     surface, dry northerly winds cleared the fog and low clouds
     from the Willamette Valley Thursday afternoon and helped
     maintain mostly clear skies overnight.  That allowed
     temperatures to drop below freezing in many wind-sheltered
     valley locations early this morning.  Salem dipped down to
     29 degrees and Eugene recorded a minimum of 30 degrees.  It
     stayed warmer where Gorge outflow kept the atmosphere well
     mixed. McMinnville never dipped below 40 degrees this
     morning, and Troutdale held in the mid 40s.

     Late-morning visible satellite imagery showed mostly clear
     skies over all of Washington and stretching from the
     northern and central Oregon coast, across the Willamette
     Valley, to over the Cascades. Low clouds and fog were
     hugging the southern Oregon coast, with pockets of fog still
     lingering in the southwestern valleys.  Many of the river
     basins in central and eastern Oregon also had areas of low
     clouds.  Clouds and fog were holdning temperatures in the
     mid 40s along the south coast and in the southwestern
     valleys.  However, sunny skies had warmed temperatures into
     the low to mid 50s from the northern and central coast
     across most of the Willamette Valley.

     The freezing levels remain near 9000 feet, so sunny skies
     and continued dry offshore flow will lift western Oregon
     temperatures well above normal again today. However, the air
     mass below 7000 feet has cooled about 5 degrees since
     Thursday, and most surface temperatures are running a couple
     of degrees cooler than 24 hours ago.  Willamette Valley
     highs today should warm to near 60 degrees, after topping
     out in the low 60s Thursday afternoon.  Ventilation
     conditions will be fair this afternoon, with surface warming
     lifting mixing heights above 2000 feet.  However,
     northeasterly transport winds are not favorable for
     evacuating smoke from stack burns.

Surface Winds:
     NNE 5-15 this afternoon.
Transport Winds:
     NE 12 this afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height today will be near 2500 feet.  Ventilation index 30.
High Temperature:
     Salem\'s high temperature today will be near 60.
Humidities:
     Minimum relative humidity will be near 35%.
Sunrise/Sunset:
     Salem sunset tonight: 5:46pm; sunrise tomorrow: 7:05am.

Extended Outlook:
     Northeasterly flow aloft is forecast to drive slightly
     cooler air into northern Oregon over the weekend, with
     morning minimums, once again, locally dipping below
     freezing.  Plenty of sunshine will help afternoon highs
     recover into the mid 50s, across the valley, with
     downsloping offshore flow helping coastal temperaturse
     locally climb to around 60 degrees. Brisk easterly winds
     will continue to pour out from the western end of the
     Columbia Gorge into the extreme north valley.

     The upper-level ridge is forecast to finally push inland,
     over Oregon, Monday.  Warming aloft will help afternoon
     temperatures climb a few more degrees, with continued
     spring-like conditions across the region.  A weakening
     weather system may begin spreading high clouds into the
     regin by Monday night.  Long-range computer models differ on
     the strength of weather systems trying to break through the
     ridge of high pressure and come onshore next week.  Some
     models bring rain onshore as early as Tuesday, while others
     keep it dry all week.  The latest guidance is showing a
     chance of rain Tuesday through at least Friday of next week,
     as the flow aloft turns southwesterly.

Tomorrow (20 Feb):  Sunny and Slightly Cooler.  29/56

Sun (21 Feb):  Sunny.  Cool Start with Near Normal Afternoon Temperatures.  28/55

Mon (22 Feb):  Mostly Sunny.  A Touch Warmer.  30/59

Tue (23 Feb):  Increasing Clouds.  Chance of Light Rain.  35/55

Wed (24 Feb):  Chance of Rain.  Snow Level near 4000 Feet.  38/55

Thu (25 Feb):  Mostly Cloudy.  Chance of Rain.  Snow Level 4-5000 Feet.  40/54

Fri (26 Feb):  Mostly Cloudy.  Chance of Rain.  Snow Level near 5000 Feet.  40/55

ODA Meteorologist
weather at oda.state.or.us