[willamette-fcst] Forecast - Tuesday, September 29th, 2009

Tue Sep 29 09:00:35 PDT 2009

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, September 29th, 2009 at 9:00am.

Burn Advisory:
     Agricultural burning is allowed.  Suggested burn times are from 12:00pm until 6:00pm.
     Preparatory burning is not allowed.
     Propane flaming is allowed from 12:00pm until 6:00pm.
     Stack burning is not allowed.

Weather Discussion:
     A Pacific cold front swept across western Oregon Monday and
     was pushing into Idaho this morning. Rainfall amounts in the
     Willamette Valley were generally around one-tenth of an inch
     or less, with the greatest totals in Lane County.

     Satellite imagery showed a few instability showers rotating
     onshore this morning, in the wake of the cold front, with an
     impressive line of showers just off the coastline. An
     upper-level trough will move onshore this afternoon, along
     with widespead showers and a chance of thundershowers. The
     snow level will drop to the Cascade passes today, with the
     freezing levels measured over Salem and Medford this morning
     at just 5200 and 5700 feet respectively.

     Ventilations conditions should be good this afternoon, with
     southwesterly transport winds and mixing heights climbing to
     nearly 5000 feet. However, the incoming showers will likely
     keep things too damp for burning. We are not aware of any
     available fields for preparatory or open burning at this
     time. With the exception of propane flaming, the summer
     field-burning season is likely over. 

Surface Winds:
     S 5-15 this morning, W 7-15 this afternoon.
Transport Winds:
     SSW 15 this morning, W 15 this afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height today will be near 5000 feet.  Ventilation index 75.
High Temperature:
     Salem\'s high temperature today will be near 60.
Humidities:
     Minimum relative humidity will be near 60%.
Sunrise/Sunset:
     Salem sunset tonight: 6:56pm; sunrise tomorrow: 7:09am.

Extended Outlook:
     A transitory weak upper-level ridge is forecast to bring
     some drying and minor warming on Wednesday.  Another cold
     front is forecast to move mainly into western Washington on
     Thursday, but the trailing edge of the front may bring some
     light rain to extreme northwestern Oregon. A cold
     upper-level trough is forecast to drop southward over the
     region Friday and Saturday.  Showers will likely spread
     southward across Washington and extreme northern Oregon
     Friday and all of Oregon by Saturday.  Snow levels will drop
     to the Cascade passes Saturday.

     The upper-level trough is forecast shift east of the
     Cascades Sunday and into Idaho on Monday.  A progressively
     drier, but continued cool, north-northeasterly flow aloft
     will make for chilly nights and crisp days.  An upper-level
     ridge will slowly build into the coastline next week, with
     moderating daytime temperatures.

Tomorrow (30 Sep):  Showers Ending Early...Becoming Partly Cloudy.  44/63

Thu (01 Oct):  Increasing Clouds.  Slight Chance of Light Rain North.  44/67

Fri (02 Oct):  Mostly Cloudy.  Chance of Showers...Mainly North.  47/66

Sat (03 Oct):  Showers Likely.  Snow Level Dropping to 4000 Feet.  45/60

Sun (04 Oct):  Mostly Cloudy and Cool. Slight Chance of Showers.  43/64

Mon (05 Oct):  Partly Sunny.  42/66

Tue (06 Oct):  Mostly Sunny and Warmer.  42/70

ODA Meteorologist
weather at oda.state.or.us