[willamette-fcst] Forecast - Tuesday, February 16th, 2010

[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, February 16th, 2010 at 12:00pm.

Burn Advisory:
     Recommended burn times for agricultural burning are from now to 3:30pm.
     Stack burning is not allowed.

Weather Discussion:
     The main cloud-shield and areas of rain, associated with the weakening cold front that
     spread rain across western Oregon overnight, was pushing east, into Idaho, late this
     morning.  Satellite imagery and surface reports showed some breaks in the clouds across
     western Oregon.  Doppler radar showed that the showers were ending west of the Cascades.
 
     Much of the Willamette Valley picked up about one-quarter of an inch of rain overnight,
     with up to three-quaters of an inch falling along the north coast.  Areas of light rain
     fell over central and eastern Oregon earlier this morning, with most areas picking up
     only a few hundredths of an inch.  The rainfall was also tapering off east of the
     Cascades by late this morning, with most of the remaining activity near the Idaho border.

     The air mass is very mild, with the freezing level above 7000 feet.  ODOT road cameras
     showed wet pavement over the Cascade passes with late-morning pass temperatures in the low
     to mid 40s.  Willamette Valley temperatures stayed in the mid to upper 40s overnight and
     had already warmed into the mid to upper 50s by late this morning.  Coastal readings were
     slightly cooler...in the low to mid 50s.

     High pressure will rapidly build over the region today, with warming aloft capping any
     convection due to daytime heating.  Partly sunny skies will combine with the higher
     sun-angle of the second half of February to lift valley temperatures to around 60 degrees
     this afternoon.  Northerly transport winds are not favorable for stack burning, so it was
     not allowed today.  Clearing skies and light north winds will help temperatures to drop
     into the mid to upper 30s across the Willamette Valley tonight with areas of fog forming.

Surface Winds:
     Becoming N 3-8 this afternoon.
Transport Winds:
     Becoming N 5 this afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height today will be near 2000 feet.  Ventilation index 12.
High Temperature:
     Salem\'s high temperature today will be near 60.
Humidities:
     Minimum relative humidity will be near 55%.
Sunrise/Sunset:
     Salem sunset tonight: 5:42pm; sunrise tomorrow: 7:10am.

Extended Outlook:
     An upper-level ridge of high pressure is forecast to amplify, just off the west coast
     Wednesday and Thursday, with a dry northerly flow aloft developing over Oregon.
     Increasing offshore flow at the surface will help to clear skies and limit AM fog,
     especially in the north valley.  Easterly winds will become quite strong, at the western
     end of the Columbia Gorge, by early Thursday morning.

     Drier air will make for a greater temperature spread between overnight minimums and
     daytime maximums.  After starting off in the 30s, valley highs should climb to around
     60 degrees. The air mass puring into the Columbia Basin, from Canada, will likely be cool
     enough to keep Willamette Valley temperatures from climbing much above 60 degrees.
     However, the offshore flow, down-sloping off the coastal range, may send coastal
     temperatures into the mid 60s by Thursday.

     Some moisture may undercut the upper-level ridge and begin moving into southern Oregon
     late in the week.  It is possible that moisture could advance northward, into the
     Willamette Valley, by the weekend, with an increasing chance of rain early next week.

Tomorrow (17 Feb):  Areas of AM Fog...Mainly Central and South.  Partly Cloudy.  34/58

Thu (18 Feb):  Patchy AM Fog...Mainly South.  Mostly Sunny and Mild.  34/62

Fri (19 Feb):  Partly Cloudy and Mild with Continued Offshore Flow.  35/60

Sat (20 Feb):  Increasing Clouds.  Slight Chance of Rain...Mainly South.  34/58

Sun (21 Feb):  Mostly Cloudy.  Chance of Rain...Mainly South.  36/55

Mon (22 Feb):  Chance of Rain.  38/54

Tue (23 Feb):  Chance of Rain.  40/54

ODA Meteorologist
weather at oda.state.or.us