[willamette-fcst] Forecast - Friday, October 3rd, 2008

Fri Oct 3 08:04:29 PDT 2008

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, October 3rd, 2008 at 9:00am.

Burn Advisory:
     Agricultural burning is allowed.  Suggested burn times are from 8:00am until 5:00pm.
     Preparatory burning is not allowed.
     Propane flaming is not allowed.
     Stack burning is not allowed.

Weather Discussion:
     The first in a series of Pacific storms brought an end to
     the recent dry and warm spell with about one-tenth of an
     inch of rain falling across much of the Willamette Valley in
     the 24-hour period ending at 5am today.  Areas of few light
     rain were falling this morning across Western Oregon, in
     advance of a very impressive weather system forecast to
     bring increasing rain and wind to the region later today.

     A rapidly intensifying low-pressure center was about 500
     miles off the Central Oregon Coast this morning and is
     forecast to track close enough to the coastline to bring
     strong southerly winds to the coastal strip beginning about
     mid-afternoon today.  This system has also entrained
     tropical moisture and may bring close to an inch of rain to
     the Willamette Valley between now and Saturday afternoon,
     with greater amounts along the coast and in the coastal range.

     Satellite imagery showed a solid and developing cloud-shield
     spreading over Washington and Oregon and extending more than
     200 miles offshore.  Doppler radar showed a band of rain
     moving northward over the Northern Willamette Valley with
     some breaks in the steady precipitation over the south
     valley and SW Oregon.  There will likely be some let-up in
     the rain later this morning, before it increases again later
     this afternoon.

     Even with some rain showers, high tempertures climbed into
     the low 70s across most of the Willamette Valley Thursday. 
     The Salem sounding this morning showed considerable cooling,
     below 10,000 feet, compared with Thursday afternoon, so
     temperatures should not make it out of the 60s today.  Some
     warming aloft is forecast this aftenoon, ahead of the
     approaching storm, so mixing heights will stay below 3000
     feet today.  Conditions are too damp for burning.

     The first significant cold front of autumn is forecast to
     move across Western Oregon overnight, with locally heavy
     rain and windy conditions. South winds could gust to near 60
     mph along the coast late today and tonight and to near 35
     mph in the Willamette Valley Saturday morning.  Steady rain
     will turn to showers by Saturday afternoon, and the brisk
     southerly winds will slowly decrease.

Surface Winds:
     SE 5-15 this morning, SE 10-20 this afternoon.
Transport Winds:
     SSE 10 this morning, S 20 this afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height today will be near 2500 feet.  Ventilation index 50.
High Temperature:
     Salem\'s high temperature today will be near 66.
Humidities:
     Minimum relative humidity will be near 70%.
Sunrise/Sunset:
     Salem sunset tonight: 6:48pm; sunrise tomorrow: 7:15am.

Extended Outlook:
     A transitory ridge of high pressure is forecast to bring
     some drying Sunday.  There are already differences in the
     computer model forecasts, by Monday, regarding the timing of
     the next weather system.  It is forecast to come onshore
     sometime between Monday morning and Monday evening.  If it
     holds off until late in the day, it could create favorable
     winds for burning, but fields will likely be too damp from
     the weekend rains.  A cool upper-level trough is forecast to
     bring showers to the region through early Wednesday.

     All of the computer models are forecasting some drying
     around Thursday of next week with a strong ridge building
     somewhere near the west coast by next weekend.  If that
     ridge builds directly over the Pacific Northwest, damp
     fields would have a chance to dry enough, for possible
     burning, ahead of storms slated to come onshore the
     following week.

Tomorrow (04 Oct):  Showers and Blustery.  Wind: S 15-25 G35..Decreasing Late.  54/63

Sun (05 Oct):  Mostly Cloudy.  Slight Chance of a Shower.  48/65

Mon (06 Oct):  Mostly Cloudy.  Chance of Rain Late.  46/68

Tue (07 Oct):  Light Rain Turning to Showers.  50/63

Wed (08 Oct):  Decreasing Showers.  45/62

Thu (09 Oct):  Partly Sunny.  42/67

Fri (10 Oct):  Partly Sunny.  42/67

ODA Meteorologist
weather at oda.state.or.us