[willamette-fcst] Forecast - Wednesday, August 12th, 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, August 12th, 2009 at 8:50am.

Burn Advisory:
     Agricultural burning is allowed.  Suggested burn times are from 1:00pm until 6:00pm.
     Preparatory burning is not allowed.
     Propane flaming is not allowed.
     Straw stack burning is allowed, for dry stacks, from 1:00pm until 6:00pm.

Weather Discussion:
     An impressive Pacific frontal system, for mid-August, spread
     rain across northwestern Oregon late Tuesday through the
     overnight period. Rainfall amounts varied greatly, from
     north to south, across the Willamette Valley. The Portland
     area locally picked up over three-quarters of an inch of
     rain, with only sprinkles falling over portions of Lane
     County. Rainfall in Marion and northern Linn Counties was
     generally around one-tenth of an inch, with lighter amounts
     in southern Linn County.

     The front was over extreme northwestern Oregon at
     mid-morning with light rain falling along the north coast
     and in the northern Willamette Valley, generally north of
     Marion County. Radar showed the main area of rain moving
     northeast of the Willamette Valley with very little activity
     movning onshore.  Satellite imagery showed mostly cloudy
     skies covering the valley, with some thin spots in the
     clouds over much of the south valley.  Cloudy skies kept
     temperatures generally in the muggy 60s overnight wit
     mid-morning readings in the mid to upper 60s.

     The front is forecast to slowly sag southward today,
     maintaining mostly cloudy skies over the Willamette Valley
     with a chance of light rain at times...mainly north.
     Continued onshore flow and cooler air aloft will combine to
     keep high temperatures from climbing much above the mid 70s
     (about 10 degrees below normal).

     Forecast southwesterly transport winds are favorable for
     burning, but fields are likely too damp for burning in the
     north valley. If the south valley stays dry, and there is
     enough afternoon warming to lift mixing heights above 3000
     feet, then open burning there may be possible.

Surface Winds:
     S 5-10 this morning, W 5-12 this afternoon.
Transport Winds:
     S 12 this morning, SW 15 this afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height today will be near 3500 feet.  Ventilation index 53.
High Temperature:
     Salem\'s high temperature today will be near 75.
Humidities:
     Minimum relative humidity will be near 56%.
Sunrise/Sunset:
     Salem sunset tonight: 8:22pm; sunrise tomorrow: 6:12am.

Extended Outlook:
     An upper-level trough is forecast to follow the cold front
     onshore Thursday and could bring a few more showers to
     mainly the northern Willamette Valley.  Onshore flow and
     colder air aloft will keep temperatures well below
     mid-August normals.  If fields are dry enough, and if
     surface winds do not become too strong, the passage of the
     upper-level trough could create a burning opportunity.

     A drier northwesterly flow aloft is forecast to move over
     western Oregon Friday and Saturday.  The flow is forecast to
     become northerly by Sunday, and offshore early next week,
     with more sunshine and warmer temperatures.  Near-record
     warm temperatures are possible by next Tuesday, with a very
     strong upper-level ridge forecast to build over the region.

Tomorrow (13 Aug):  Mostly Cloudy.  Chance of Light Showers...Mainly North.  56/74

Fri (14 Aug):  Morning Clouds...Clearing Skies in the Afternoon.  50/78

Sat (15 Aug):  Mostly Sunny.  49/80

Sun (16 Aug):  Sunny and Warmer.  51/85

Mon (17 Aug):  Sunny and Very Warm.  54/90

Tue (18 Aug):  Sunny and Very Warm.  58/95

Wed (19 Aug):  Mostly Sunny and Warm.  58/91

ODA Meteorologist
weather at oda.state.or.us