[willamette-fcst] Forecast - Monday, March 15th, 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: 
     Monday, March 15th, 2010 at 9:00am.

Burn Advisory:
     Recommended burn times for agricultural burning are from 10:00am until 4:30pm.
     Stack burning is not allowed.

Weather Discussion:
     An upper-level ridge of high pressure brought drying and
     warming over the weekend.  However, the transition to a
     drier air mass allowed Willamette Valley temperatures to
     locally drop to near freezing Saturday morning and below the
     freezing mark Sunday morning.  Eugene recorded a minimum
     Saturday morning of 32 degrees and a low temperature Sunday
     morning of 30 degrees.  Salem and McMinnville also dipped
     down to 30 degrees Sunday morning, and Hillsboro dropped to
     29 degrees.  The air mass aloft warmed significantly Sunday
     afternoon, with the freezing level rising to around 9000
     feet.  Willamette Valley high temperatures finally climbed
     to near-normal, for the first time in a week.

     A weak warm front brought some sprinkles to northwestern
     Oregon overnight and early this morning, with some very light
     rain making it into the northern Willamette Valley. 
     Rainfall amounts were not measurable in the valley, but the
     north coast picked up a few hundredths of an inch.  By
     mid-morning, Doppler radar showed that the shower activity
     had pretty much ended across northwestern Oregon, with
     possibly a few lingering sprinkles over the western slopes
     of the extreme northern Cascades and just off the north coast.

     Satellite imagery, at mid-morning, showed considerable middle and
     high clouds covering all of Washington and most of Oregon.  Skies
     were sunny over the southeastern corner of the state. Temperatures
     ranged from the upper 30s to the upper 40s across western Oregon
     and from the mid 20s to the mid 30s east of the Cascades.  Winds
     were light statewide except for easterly gusts to near 30 mph at
     the western end of the Columbia Gorge.

     The ODA surface analysis showed weak offshore gradients, in
     response to a developing storm system more than 500 miles
     off the northern California coast.  As that system develops,
     it will force the warm front further north, into southwestern
     British Columbia.  The air aloft will continue to warm over
     Oregon.  The freezing levels should jump to above 10,000 feet
     this afternoon.  Considerble middle and high clouds will remain
     over western Oregon today.  Combined with poor mixing of the air
     mass, filtering of the sunshine will keep temperatures from climbing
     as high as they otherwise might this afternoon.  High temperatures
     should still make it into the low 60s across the Willamette Valley,
     which will be about 5 degrees above normal for a change.

Surface Winds:
     NE 0-5 this morning, N 3-8 this afternoon.
Transport Winds:
     NE 5 this morning, NE 5 this afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height today will be near 1500 feet.  Ventilation index 8.
High Temperature:
     Salem\'s high temperature today will be near 63.
Humidities:
     Minimum relative humidity will be near 46%.
Sunrise/Sunset:
     Salem sunset tonight: 7:18pm; sunrise tomorrow: 7:23am.

Extended Outlook:
     Tonight should be a mild one, with clouds continuing to
     lower and thicken in advance of the next wather system.  A
     cold front is forecast to slowly move onshore Tuesday
     morning, spreading light rain back across most of western
     Oregon.  Snow levels will start out quite high but drop to near
     the Cascade passes by late Tuesday afternoon.  Willamette
     Valley highs will fall back to near normal with the weakening
     cold front bringing around one-tenth of an inch of rain.

     A cool upper-level trough will maintain some showers over
     mainly the northern half of Oregon through about midday
     Wednesday.  A cool and dry northwesterly flow aloft is
     forecast for Thursday, as an upper-level ridge of high
     pressure begins building just off the west coast.  The ridge
     is forecast by all of the long-range computer models to move
     over Oregon on Friday through the weekend.  Offshore surface
     winds, on Friday, should turn onshore over the weekend for a
     slow cooling trend.  A cold front is forecast to bring back
     some rain Sunday night and Monday.

Tomorrow (16 Mar):  Light Rain Likely and Cooler.  48/58

Wed (17 Mar):  Showers Ending...Becoming Partly Sunny in the Afternoon.  39/57

Thu (18 Mar):  Cool Start...Becoming Mostly Sunny.  34/60

Fri (19 Mar):  Sunny and Warmer.  Offshore Flow.  34/64

Sat (20 Mar):  Sunny and Mild.  Onshore Flow Returning.  36/62

Sun (21 Mar):  Increasing Clouds.  Chance of Rain Late.  39/59

Mon (22 Mar):  Rain Likely and Cooler.  39/55

ODA Meteorologist
weather at oda.state.or.us