[willamette-fcst] Forecast - Monday, August 24th, 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: 
     Monday, August 24th, 2009 at 8:55am.

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

Weather Discussion:
     A transitory upper-level ridge of high pressure is over
     Oregon this morning. Visible satellite imagery shows mostly
     clear skies over the state.  There are some low clouds
     extending from the extreme north coast up the Columbia River
     to the Portland area.  Mid-morning temperatures were mostly
     in the upper 40s and 50s statewide.  The upper-level ridge
     is forecast to shift over Idaho this afternoon, with
     increasing southwesterly flow aloft. Continued sunny skies
     should warm valley temperatures in to the low 80s this afternoon.

     Light winds forecast through early this afternoon. However,
     ventilation conditions are forecast to improve later this
     afternoon, likely allowing for open burning in both the
     north and south valley. Daytime heating should lift mixing
     heights above 4000 feet, with an approaching cold front 
     increasing the southwesterly transport winds.  The front is
     forecast to move onshore overnight, with a good chance of
     light rain along the coast and possibly some drizzle or very
     light rain in the Willamette Valley Tuesday morning...mainly
     from Salem north.

Surface Winds:
     Var 0-6 this morning, W 5-10 this afternoon.
Transport Winds:
     NE 5 this morning, SW 10 this afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height today will be near 4500 feet.  Ventilation index 45.
High Temperature:
     Salem\'s high temperature today will be near 82.
Humidities:
     Relative humidity drops to 50% by 12pm.
     Minimum relative humidity will be near 30%.
Sunrise/Sunset:
     Salem sunset tonight: 8:03pm; sunrise tomorrow: 6:26am.

Extended Outlook:
     After a chance of very light rain or drizzle the morning,
     skies should begin to clear Tuesday afternoon.  Onshore flow
     will cool valley high temperatures into the low to mid 70s. 
     The flow aloft will weaken, and turn more southerly,
     Wednesday and Thursday, as a strong upper-level ridge
     rebuilds over the region.  Temperatures should quickly warm
     back above normal, under mostly sunny skies.

     A weakening Pacific cold front is forecast to brush by to
     our north Friday, but it should be strong enough to increase
     the onshore flow and cool temperatures back to near-normal. 
     It may also create an open burning opportunity Friday
     afternoon.  The upper-level ridge is forecast to quickly
     rebuild over the region this weekend.

Tue (25 Aug):  Chance of Light AM Rain...Mainly North.  Partial Afternoon Clearing.  51/73

Wed (26 Aug):  Becoming Mostly Sunny and Warmer.  51/86

Thu (27 Aug):  Sunny and Warm.  53/87

Fri (28 Aug):  Partly Cloudy and Cooler.  54/80

Sat (29 Aug):  Sunny and Warmer.  53/87

Sun (30 Aug):  Sunny and Very Warm.  55/91

Mon (31 Aug):  Sunny and Warm.  Increasing onshore flow in the afternoon.  55/86

ODA Meteorologist
weather at oda.state.or.us