[willamette-fcst] Forecast - Thursday, August 27th, 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: 
     Thursday, August 27th, 2009 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:
     A strong upper-level ridge of high pressure, centered over
     Idaho, will bring a sunny and warmer day to the interior of
     western Oregon today. The Salem sounding this morning showed
     further warming alost, since Wednesday afternoon, so high
     temperatures will likely warm into the low 90s, after
     topping out in the mid to upper 80s Wednesday.  Mixing
     heights only climbed to around 3000 feet Wednesday and
     should be even lower today. The combinatin of light surface
     winds, weak southerly flow aloft, and low mixing heights
     will make for poor ventilation conditions over the
     Willamette Valley.

Surface Winds:
     S 2-6 this morning, SW 4-8 this afternoon.
Transport Winds:
     SSE 4 this morning, SW 5 this afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height today will be near 2700 feet.  Ventilation index 14.
High Temperature:
     Salem\'s high temperature today will be near 92.
Humidities:
     Relative humidity drops to 50% around 10am.
     Minimum relative humidity will be near 20%.
Sunrise/Sunset:
     Salem sunset tonight: 7:58pm; sunrise tomorrow: 6:30am.

Extended Outlook:
     A weakening Pacific cold front is forecast push into the
     strong ridge and swing onshore Friday.  It appears as if
     this system will have enough moisture to bring some light
     rain to the coast by Friday afternoon, with a good chance of
     light rain in the Willamette Valley by Friday evening. 
     Ahead of it, continued southerly flow aloft will likely keep
     mixing heights suppressed, over western Oregon, Friday,
     making a burning opportunity unlikely.  Increasing clouds
     and onshore flow should knock 10-15 degrees off of valley
     high temperatures Friday, compared to this afternoon.

     The incoming weather system is forecast to stall over
     Washington and Oregon this weekend...forming an upper-level
     low-pressure area over the region...cut off from the main
     circulatino pattern.  These types of systems tend to be very
     slow moving, with this one forecast to drift into eastern
     Oregon by Sunday afternoon.  That will bring slow drying and
     warming to areas west of the Cascades, while maintaining a
     good chance of showers over the eastern third of the state.

     The upper-level low-pressure area is forecast to finally
     push into Idaho Monday with weak south-southwesterly flow
     aloft returning to western Oregon during the first half of
     next week.  That should bring mostly sunny skies and above
     normal temperatures to the Willamette Valley.  The thermal
     trough is forecast to stay east of the Cascades, with weak
     onshore flow possibly allowing for some burning opportunities.

Tomorrow (28 Aug):  Increasing Clouds and Cooler.  Chance of Showers by Evening.  56/78

Sat (29 Aug):  Mostly Cloudy.  Chance of Showers...Decreasing Late.  55/78

Sun (30 Aug):  Becoming Mostly Sunny and Warmer.  53/83

Mon (31 Aug):  Mostly Sunny.  54/86

Tue (01 Sep):  Mostly Sunny.  54/88

Wed (02 Sep):  Mostly Sunny.  54/85

Thu (03 Sep):  Mostly Sunny.  53/85

ODA Meteorologist
weather at oda.state.or.us