[willamette-fcst] Forecast - Friday, July 10th, 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: 
     Friday, July 10th, 2009 at 9:00am.

Burn Advisory:
     Agricultural burning is allowed.  Suggested burn times are from 1:00pm until 7:00pm.
     Preparatory burning is not allowed.
     Propane flaming is not allowed.
     Stack burning is not allowed.

Weather Discussion:
     Mid-morning satellite imagery showed mostly clear skies east
     of the cascades, but mostly cloudy skies across western
     Oregon, due to a moist southerly flow aloft around an
     upper-level low-pressure area, centered about 200 miles off
     the southern Oregon Coast.  Doppler radar was showing some
     light shower activity, moving to the north-northwest, along
     the central coast range and over the southern Cascades. 
     With the low-pressure system offshore remaining nearly
     stationary offshore today, it will continue to feed mid and
     high-level moisture over western Oregon.  Daytime heating
     will destabilize the atmosphere and increase shower
     development this afternoon...mainly over the mountains. 
     Some showers could drift over the Willamette Valley, and
     there is even a slight chance of a thunderstorm.

     With afternoon clearing, Willamette Valley temperatures
     climbed into the mid 70s Thursday.  The Salem sounding this
     morning showed warming aloft, since Thursday, so partly
     sunny skies should help temperatures climb into the low 80s
     this afternoon.  The ODA surface analysis confirmed a
     shut-off of the onshore flow across the state with northerly
     pressure gradients.  Transport winds are forecast to remain
     northerly today.

Surface Winds:
     N 5-12 this morning, N 7-15 this afternoon.
Transport Winds:
     N 10 this morning, N 12 this afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height today will be near 4500 feet.  Ventilation index 54.
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 33%.
Sunrise/Sunset:
     Salem sunset tonight: 8:59pm; sunrise tomorrow: 5:37am.

Extended Outlook:
     The upper-level low-pressure center is forecast to remain
     off the southern Oregon Coast Saturday, with continued
     southerly fow aloft over western Oregon.  That will keep
     temperatures warm statewide, with a continued feed of mid
     and high-level moisture over the region.  Afternoon and
     evening showers and thunderstorms should develop, mainly
     over the Cascades, with the chance of showers and
     thundershowers increasing Saturday night across the
     Willamette Valley.

     The trough is forecast to move inland Sunday, with showers
     likely acrsoss most of western Oregon.  There may be enough
     instability remaining in the mid and upper levels of the
     atmosphere for thunderstorms through early Sunday, before
     the cooler onshore flow deepens and stabilizes the
     mid-levels of the air mass.  A transitory ridge is forecast
     to bring a drier northwesterly flow by Monday afternoon with
     the ridge moving over Oregon Tuesday.

     Increasing west-southwesterly flow aloft will enhance the
     onshore flow and cool temperatures back to near or slightly
     below normal Wednesday through Friday.  Transport winds are
     forecast to take on more of a westerly component, which
     could create burning opportunities.

Sat (11 Jul):  Partly Sunny and Warm.  Chance of Showers/T-Storms...Increasing Late.  57/84

Sun (12 Jul):  Mostly Cloudy and Cooler.  Good Chance of Showers/T-Storms.  55/74

Mon (13 Jul):  Clearing Skies by Afternoon.  Warmer.  54/79

Tue (14 Jul):  Mostly Sunny and Warm.  51/84

Wed (15 Jul):  Partly Cloudy with Onshore Flow Developing.  53/80

Thu (16 Jul):  Partly Cloudy.  54/81

Fri (17 Jul):  Partly Cloudy.  54/81

ODA Meteorologist
weather at oda.state.or.us