[willamette-fcst] Forecast - Wednesday, October 29th, 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 29th, 2008 at 9:00am.

Burn Advisory:
     Agricultural burning is not recommended.
     Stack burning is not allowed.

Weather Discussion:
     The large upper-level ridge of high pressure that has been
     bringing dry and unseasonably warm weather to the region is
     moving east and was centered over the Rockies this morning. 
     Increasing southwesterly flow aloft has spread middle and
     high clouds across northwestern and northcentral Oregon and
     the western half of Washington.  Marine low clouds had also
     penetrated inland, across the Willamette Valley, this
     morning with areas of fog.

     The Salem sounding this morning continued to show very warm
     air aloft with a strong temperature inversion from about
     2500-4500 feet.  Mixing heights will not climb above the
     base of that inversion this afternoon.  Very light
     southwesterly transport winds will make for poor ventilation
     conditions today.

     The ODA surface analysis showed high pressure centers over
     southeastern Oregon and over the southern Oregon coast with
     very weak pressure-gradients over the Willamette Valley. 
     Valley winds were light and variable.  Temperatures dropped
     into the upper 30s across sections of the valley early this
     morning and ranged from the upper 30s to the upper 40s at
     mid-morning.

     Satellite imagery showed a nearly stationary frontal
     boundary extending from Vancouver Island, British Columbia
     southeastward to about 300 miles off the Oregon Coast.  It
     should stay offshore today, allowing for some filtered
     afternoon sunshine to warm valley temperatures into the
     upper 50s and low 60s, much like on Tuesday.  Winds will
     stay light and variable.

Surface Winds:
     Var 0-4 this morning, Var 2-4 this afternoon.
Transport Winds:
     SW 4 this morning, SW 4 this afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height today will be near 2500 feet.  Ventilation index 10.
High Temperature:
     Salem\'s high temperature today will be near 62.
Humidities:
     Minimum relative humidity will be near 57%.
Sunrise/Sunset:
     Salem sunset tonight: 6:04pm; sunrise tomorrow: 7:49am.

Extended Outlook:
     The offshore frontal boundary will slowly move closer to the
     coastline Thursday with increasing southerly flow aloft. 
     That will further warm the air aloft and suppress mixing
     heights.  Transport winds will increase and become
     south-southeasterly.  Clouds will also increase, but the
     rain should stay offshore for one more day, before moving
     inland Thursday night.

     The first in a series of weather systems will move across
     Oregon Friday with some light rain likely in the Willamette
     Valley.  This system should lose a lot of strength, as it
     pushes into the strong ridge of high pressure, but it will
     open the door for subsequent systems to bring more
     substantial precipitation to the region.

     A stronger weather system is slated to come onshore late
     Saturday, with the main jeet stream energy aimed at northern
     California.  It should still bring increasing rain to the
     Willamette Valley Saturday night with showers and somewhat
     blustery conditions Sunday.  Another system is forecast to
     move onshore Monday.  High pressure may build into the west
     coast by late in the week, with the flow aloft drying out
     and turning northwesterly.

Tomorrow (30 Oct):  Mostly Cloudy and Very Mild.  44/66

Fri (31 Oct):  Light Rain Likely With More Seasonal Temperatures.  48/59

Sat (01 Nov):  Rain Likely by Evening. 46/56

Sun (02 Nov):  Rain Turning to Showers.  45/54

Mon (03 Nov):  Rain Likely.  42/53

Tue (04 Nov):  Decreasing Showers.  42/53

Wed (05 Nov):  Partly Sunny.  35/56

ODA Meteorologist
weather at oda.state.or.us