[willamette-fcst] Forecast - Wednesday, August 20th, 2008

[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 20th, 2008 at 9:00am.

Burn Advisory:
     Agricultural burning is not recommended.
     Preparatory burning is not allowed.
     Propane flaming is not allowed.
     Stack burning is not allowed.

Weather Discussion:
     An unseasonably strong Pacific storm system spread rain into
     Western Oregon Tuesday afternoon that continued through the
     night.  Rainfall totals along the coast ranged from nearly
     an inch at Astoria to about one-third of inch from Newport
     and North Bend. In the Willamette Valley, the heaviest
     rainfall was also in the north with the north valley getting
     about one-quarter of an inch and the south valley about
     one-tenth of an inch overnight.

     Rain aksi spread east of the Cascades overnight with up to
     one-tenth of an inch falling across North-Central and NE
     Oregon.  Satellite imagery showed generally cloudy skies
     over all of Washington and Oregon this morning.  Doppler
     radar showed considerable coverage of rainfall across
     Washingtonand the northern third of Oregon.  A line of
     showers,  associated with the surfacecold front, was pushing
     through the Willamette Valley with a break in the rain
     showing up over the northern coast range.

     The cold front was moving across the Willamette Valley at
     mid-morning and will push east of the Cascades this
     afternoon.  There will likely be a let-up in the rain, and a
     few sunbreaks, in the wake of the cold front later this
     morning.  However, a strong upper-level trough will bring
     vigorous showers to Western Oregon this afternoon through
     most of Thursday with rainfall totals across the valley
     likely tripling by Thursday night.  Temperatures will be at
     least 10 degrees below normal today.  Highs will only climb
     to near 70 with breezy southwesterly winds.

Surface Winds:
     S 10-20 this morning, SW 10-20 this afternoon.
Transport Winds:
     SSW 22 this morning, SW 25 this afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height today will be near 2000 feet.  Ventilation index 50.
High Temperature:
     Salem\'s high temperature today will be near 70.
Humidities:
     Minimum relative humidity will be near 70%.
Sunrise/Sunset:
     Salem sunset tonight: 8:09pm; sunrise tomorrow: 6:22am.

Extended Outlook:
     A strong upper-level trough will keep the showers going
     through Thursday.  Total rainfall amounts, since Tuesday
     evening, will likely be one-half to one inch in the north
     valley and one-quarter to three-quarters of an inch in the
     south valley.   Some locations...especially near the Cascade
     foothills, may get over an inch.

     A flat transitory ridge of high pressure will dry things out
     and warm temperatures back to near normal Friday with some
     sunshine.  The flow aloft will turn southwesterly Saturday
     in response to a large upper-level trough in the Gulf of
     Alaska.  That will bring further warming to Western Oregon,
     which will air in the drying of damp fields.  The
     upper-level trough is forcast to move closer to the
     coastline Sunday with increasing southwesterly flow aloft. 
     That will likely increase the onshore flow Sunday afternoon
     with high temperatures staying in the 80s. 

     A Pacific cold front is forecast to come onshore Monday that
     could bring another quarter-inch or more of rain to the
     Willamette Valley...especially north.  The current timing of
     this system is too quick for a burning opportunity Monday,
     before the rain sets in, but that will need to be watched
     closely.  Another flat ridge will dry and warm the air mass
     Tuesday with the flow aloft turning soutwesterly again Wednesday.

Tomorrow (21 Aug):  Mostly Cloudy.  Showers Likely...Mainly North.  56/71

Fri (22 Aug):  Mostly Sunny & Warmer.  50/80

Sat (23 Aug):  Sunny and Warm.  52/85

Sun (24 Aug):  Mostly Sunny.  Increasing Clouds Late.  54/85

Mon (25 Aug):  Good Chance of Rain and Cooler.  58/72

Tue (26 Aug):  Partly Cloudy and Warmer.  50/78

Wed (27 Aug):  Mostly Sunny Early...Increasing Clouds with a Chance of Rain Late.  53/81

ODA Meteorologist
weather at oda.state.or.us