[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.

Issued: 
     Friday, February 19th, 2010 at 9:00am.

Burn Advisory:
     Recommended burn times for agricultural burning are from 12:00pm to 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 over Oregon.  On the surface,
     increasing northerly winds brought enough dry air into the
     Willamette Valley to completely clear the fog and low
     clouds, Thursday afternoon, with high temperatures climbing
     into the upper 50s and low 60s.  Skies remained clear
     overnight, north of about Roseburg, with the air mass
     staying too dry for fog formation in the Willamette Valley. 
     Low temperatures dropped below freezing in many
     wind-sheltered areas but held in the upper 30s and low 40s,
     where Gorge outflow kept the atmosphere well mixed.

     Visible satellite this morning showed fog and low clouds
     across the valleys of southwestern Oregon, the southern
     Oregon coast, and many of the basins east of the Cascades. 
     Skies were mostly clear across northwestern
     Oregon...including over the entire Willamette Valley. 
     Valley temperatures ranged from the low 30s, in Eugene, to
     the mid 40s in Aurora and McMinnville.  Coastal temperatures
     ranged from the mid 30s at Astoria to the mid 40s at Newport.

     The air aloft is several degrees cooler today, below 7000
     feet, compared to Thursday morning.  However, the freezing
     levels remain near 9000 feet.  Sunny skies and continued dry
     offshore flow will combine to lift western Oregon
     temperatures into the mid to upper 50s this
     afternoon...about 5 degrees cooler than yesterday but still
     above normal.  Ventilation conditions will become fair this
     afternoon, but northeasterly transport winds are not
     favorable for evacuating smoke from stack burns.

Surface Winds:
     NNE 5-12 this morning, NNE 5-15 this afternoon.
Transport Winds:
     NNE 7 this morning, 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 57.
Humidities:
     Minimum relative humidity will be near 38%.
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, and to near 60
     along the central coast, with continued offshore flow. 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 degrees above normal.  A weakending
     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.  I will split the difference, for now,
     and call for a chance of rain, beginning Tuesday, with an
     increasing chance of rain later next week.

Tomorrow (20 Feb):  Sunny and Slightly Cooler.  29/54

Sun (21 Feb):  Sunny.  Cool Start with Near Normal Afternoon Temperatures.  28/53

Mon (22 Feb):  Moslty Sunny.  A Little Warmer.  30/57

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