[willamette-fcst] Forecast - Tuesday, July 31st, 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: 
     Tuesday, July 31st, 2007 at 9:00am.

Burn Advisory:
     Agricultural burning is not recommended.
     Preparatory burning is allowed from 11:00am until 3:00pm with a 100 acre limit.
     Propane flaming is allowed from 11:00am until 5:00pm.
     Stack burning is not allowed.

Weather Discussion:
     An upper-level ridge of high pressure will briefly build
     over the Pacific Northwest today and Wednesday, with sunny
     and warmer weather for most of the region.  At the surface,
     high pressure is building into Southern British Columbia,
     Washington, and Northern Oregon, while a thermal trough of
     low pressure is strengthening over Northern California and
     Nevada.  That is resulting in northerly low-level flow
     across Western Oregon, which is inhibiting the development
     of moring marine clouds in the Willamette Valley.

     North winds will increase this afternoon, in the Willamette
     Valley, and relative humidities will drop below 30%.

     ...Fire Marshal Conditions will likely be met for prep
     burning around 3pm, and may be met for propane flaming
     around 5pm...

     Mixing heights should climb to near 3000 feet by 11am but
     will only reach about 4500 feet this afternoon, due to
     continued warming aloft.  Temperatures will climb into the
     mid to upper 80s this afternoon and into the low to mid
     90s Wednesday afternoon.

Surface Winds:
     N 8-12 this morning, N 10-15 G20 this afternoon.
Transport Winds:
     NNE 15 this morning, NNE 20 this afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height today will be near 4500 feet.  Ventilation index 90.
High Temperature:
     Salem\'s high temperature today will be near 87.
Humidities:
     Relative humidity drops to 50% by 11am.
     Minimum relative humidity will be near 25%.
Sunrise/Sunset:
     Salem sunset tonight: 8:40pm; sunrise tomorrow: 5:57am.

Extended Outlook:
     There are no major changes in the long-range forecast.  The
     upper-level ridge, and associated surface thermal trough,
     are still forecast to shift eastward on Thursday, as a
     rather strong weather system, for early August, approaches
     the coastline.  Transport winds will likely shift from
     northerly to northwesterly Thursday afternoon and evening,
     while the mixing heights rise in advance of the upper-level
     trough.  The timing of this change is crucial, as to whether
     it will create a burning opportunity.  We will continue to
     monitor the situation and keep you updated.

     A cool upper-level trough is forecast to drop over the
     Pacific Northwest Friday through the weekend.  That will
     produce strong onshore flow, cool tempertures, and the
     chance for light showers in the Willamette Valley.  The
     trough pulls out of the region Monday for drying and warming
     conditions.

Tomorrow (01 Aug):  Sunny and Hot.  55/93

Thu (02 Aug):  Sunny. Increasing Clouds Late.  60/88

Fri (03 Aug):  Mostly Cloudy and Cooler.  55/78

Sat (04 Aug):  Mostly Cloudy.  Chance of Drizzle or Light Showers.  55/73

Sun (05 Aug):  Mostly Cloudy.  Chance of Drizzle or Light Showers.  55/72

Mon (06 Aug):  Morning Clouds...Afternoon Clearing.  53/78

Tue (07 Aug):  Morning Clouds...Mostly Sunny.  51/81

ODA Meteorologist
weather at oda.state.or.us