[willamette-fcst] Forecast - Wednesday, October 1st, 2008

[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: 
     Wednesday, October 1st, 2008 at 9:00am.

Burn Advisory:
     Agricultural burning is allowed.  Suggested burn times are from 12:00pm until 5:00pm.
     Preparatory burning is not allowed.
     Propane flaming is not allowed.
     Stack burning is not allowed.

Weather Discussion:
     The strong upper-level ridge of high pressure over the
     Pacific Northwest will continue to move east today with an
     increasing south-southeasterly flow aloft sending mainly
     middle and high clouds over Western Oregon today.  The Salem
     sounding this morning was very similar to Tuesday morning,
     so temperatures should climb to near 80 degrees in the
     valley again this afternoon. 

     Satellite imagery showed a low pressure center about 500
     miles off the Northern California Coast with a band of
     clouds circulating around it offshore.  Some middle and high
     clouds were already spreading across Western Oregon and
     should continue to increase during the day.  As this system
     slowly moves closer to the coastline, the southerly flow
     aloft will increase this afternoon.

     The ODA surface analysis showed surface thermal trough has
     weakened over the Willamette Valley this morning and is
     forecast to further weaken today with light southerly
     gradients expected across the valley this afternoon.  Slight
     cooling aloft will combine with daytime heating to lift
     mixing heights to near 3500 feet by late this afternoon.

     Field burning is finished for the season in the Southern
     Willamette Valley. There may be limited open burning, in the
     north valley, later this afternoon, if transport winds are
     not too southerly. With rain forecast for Thursday and
     beyond, today will likely be the last field-burning
     opportunity for this season.

Surface Winds:
     S 5 this morning, SSW 5-10 this afternoon.
Transport Winds:
     S 5 this morning, SSW 9 this afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height today will be near 3500 feet.  Ventilation index 32.
High Temperature:
     Salem\'s high temperature today will be near 80.
Humidities:
     Relative humidity drops to 50% by 12pm.
     Minimum relative humidity will be near 36%.
Sunrise/Sunset:
     Salem sunset tonight: 6:52pm; sunrise tomorrow: 7:12am.

Extended Outlook:
     The first in a series of weather systems is forecast to come
     onshore early Thursday with rain likely by Thursday
     afternoon across the Willamette Valley.  A more potent
     system is forecast to come onshore late Friday with heavier
     rain and perhaps strong southerly winds...especially along
     the coast.  Rain will turn to showers Saturday with total
     rainfal amounts possibly exceeding one inch in the valley.

     A transitory ridge of high pressure may bring some drying
     Sunday and Monday, ahead of the next rain-maker on Tuesday.
     Another ridge of high pressure may dry things out for at
     least a couple of days beginning Wednesday of next week.

Tomorrow (02 Oct):  Cloudy and Much Cooler.  Light Rain Likely by Afternoon.  55/66

Fri (03 Oct):  Mostly Cloudy.  Increasing Rain and Wind Late.  52/66

Sat (04 Oct):  Rain Turning to Showers and Blustery.  51/63

Sun (05 Oct):  Mostly Cloudy.  Chance of Light Rain.  49/64

Mon (06 Oct):  Mostly Cloudy.  47/69

Tue (07 Oct):  Light Rain Likely.  49/64

Wed (08 Oct):  Partly Sunny.  45/68

ODA Meteorologist
weather at oda.state.or.us