[willamette-fcst] Forecast - Friday, July 6th, 2007

[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: 
     Friday, July 6th, 2007 at 9:00am.

Burn Advisory:
     Agricultural burning is allowed.  Suggested burn times are from 12:00pm until 7:00pm.
     Stack burning is not allowed.

Weather Discussion:
     The strong upper-level ridge of high pressure, that has been
     responsible for the hot weather this week, has shifted
     eastward into Montana, with a southwesterly flow aloft over
     Oregon.  The air mass over Southern Oregon is unstable, and
     a weak weather disturbance cutting across that region will
     likely produce some thunderstorms this afternoon across
     South-Central and Southwest Oregon.  The remainder of the
     state will be dry with increasing onshore surface
     gradients.

     The ODA surface analyis this morning showed the thermal
     trough had shifted to near the Idaho border, with onshore
     flow across all but extreme Eastern Oregon.  That will
     spread cooler marine air across the state today.  High
     temperatures will be 5-10 degrees cooler today in the
     Willamette Valley, with sunny skies.  Central Oregon will
     cool about 10 degrees from the 100+ readings on Thursday. 
     Eastern Oregon will be the last place to see the cooling,
     with some eastern valley locations still topping 100 degrees
     today, after record-breaking heat on Thursday.

     The sounding over Salem this morning showed cooling
     thoughout the lowest 10,000 feet of the atmosphere, and more
     mid-level cooling is forecast today.  That will lift mixing
     heights to at least 4500 feet this afternoon.  Stack burning
     is not allowed, however, due to northerly gradients. 

Surface Winds:
     NNW 7-10 this morning, NNW 10-15 this afternoon.
Transport Winds:
     N 12 this morning, N 15 this afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height today will be near 4500 feet.  Ventilation index 68.
High Temperature:
     Salem\'s high temperature today will be near 82.
Humidities:
     Relative humidity drops to 50% by 2pm.
     Minimum relative humidity will be near 35%.
Sunrise/Sunset:
     Salem sunset tonight: 9:01pm; sunrise tomorrow: 5:33am.

Extended Outlook:
     It looks like it will be a fabulous weekend weather-wise
     across the state. A dry and stable westerly flow aloft will
     prevail over the weekend, with onshore surface gradients
     helping to keep temperatures near normal statewide.

     Another strong upper-level ridge will build from Eastern
     Nevada into Southern British Columbia early next week,
     bringing a return of the heat to the Pacific Northwest. 
     Surface gradients will become more northerly across Oregon
     on Monday with possible thermal trough development in the
     Willamette Valley by Tuesday.

     An upper-level low pressure area is also forecast to
     position itself off of the California Coastline next week,
     which will circulate mid and high-level moisture into Oregon
     for an increasing thunderstorm threat.  The whole pattern is
     forecast to shift eastward Thurday and Friday, with strong
     southerly flow aloft over Oregon and high thundershower
     potential.

Tomorrow (07 Jul):  Morning Clouds...Sunny.  51/80

Sun (08 Jul):  Morning Clouds...Sunny.  49/82

Mon (09 Jul):  Sunny.  52/86

Tue (10 Jul):  Mostly Sunny & Hot.  56/92

Wed (11 Jul):  Partly Cloudy, Muggy & Hot. Slight Chance of a Thundershower. 59/94

Thu (12 Jul):  Mostly Cloudy and Muggy.  Good Chance of Thundershowers.  60/88

Fri (13 Jul):  Mostly Cloudy and Much Cooler.  Chance of Showers.  57/72



ODA Meteorologist
weather at oda.state.or.us