[willamette-fcst] Forecast - Wednesday, October 21st, 2009

[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 21st, 2009 at 9:00am.

Burn Advisory:
     Agricultural burning is allowed.  Suggested burn times are from now until 4:30pm.
     Straw stack burning is allowed, for dry stacks, from now until 4:30pm.

Weather Discussion:
     Cloudy skies held temperatures mostly in the upper 40s and
     low 50s overnight across western Oregon.  Rain moved onshore
     in the pre-dawn hours this morning, ahead of a cold front
     that was just off the coastline at mid-morning.  The air
     mass was unstable enough for widespread thunderstorm
     development from the south-central coast to the southwestern
     Willamette Valley.  There was considerable lightning and
     thunder this morning from Corvallis, to Eugene, to Roseburg
     and around North Bend, on the south coast.  Doppler radar,
     at mid-morning, showed the strongest shower cells moving
     east, into the Cascades, with lighter rain moving onshore.

     Rainfall amounts were greatest along the coast this morning,
     where some locations picked up around one-half of an inch. 
     Most western valley locations received around one-tenth of
     an inch, with local spots getting close to one-quarter of an
     inch.  Areas of light rain were making it east of the
     Cascades at mid-morning...especially across north-central
     Oregon.  Lightning detection was also indicating that a few
     thunderstorms were developing, well ahead of the cold front,
     over northeastern Oregon.

     The cold front is forecast to continue to bring light rain
     to western Oregon this morning.  Rain will turn to showers,
     as the front pushes east of the Cascades this afternoon. 
     Additional rainfall amounts across the valley should be
     around one-tenth of an inch or less.  Southerly winds should
     turn more westerly, in the wake of the cold front, by late
     this afternoon.  The air aloft is still warm enough to
     support high temperatuers climbing into the lower 60s this
     afternoon...especially if there are many breaks in the
     clouds.  The freezing level was measured over Salem this
     morning at 10,700 feet and is forecast to drop only to about
     8000 feet this afternoon.  Higher mixing heights and brisk
     transport winds will make for much-improved ventilation
     conditions today. 


Surface Winds:
     S 5-15 this morning, W 5-12 this afternoon.
Transport Winds:
     S 15 this morning, W 12 this afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height today will be near 4500 feet.  Ventilation index 68.
High Temperature:
     Salem\'s high temperature today will be near 63.
Humidities:
     Minimum relative humidity will be near 65%.
Sunrise/Sunset:
     Salem sunset tonight: 6:17pm; sunrise tomorrow: 7:37am.

Extended Outlook:
     Another transitory ridge of high pressure will bring a
     return of dry weather Thursday with widespread morning fog
     giving way to partly sunny skies in the afternoon.  The next
     weather system is also forecast to push mainly into the
     southern British Columbia on Friday, but the trailing cold
     front should bring at least some light rain to western
     Oregon late in the day.  A shower or two may linger into
     Saturday morning, with some clearing Saturday afternoon.

     The next weather system is forecast to swing more rain
     onshore by Sunday evening.  As the main storm track sags
     southward, to move over Washington and Oregon, snow levels
     should drop to the Cascade passes by Monday afternoon.

Tomorrow (22 Oct):  AM Fog and Low Clouds.  Partly Sunny in the Afternoon.  45/64

Fri (23 Oct):  Areas of AM Fog.  Increasing Clouds.  PM Rain Developing.  43/62

Sat (24 Oct):  Slight Chance AM Shower.  Partly Sunny in the Afternoon.  45/62

Sun (25 Oct):  Areas of AM Fog.  Increasing Clouds.  Chance of Rain by Afternoon.  42/60

Mon (26 Oct):  Rain at Times.  Snow Level Dropping to 4000 Feet.  43/57

Tue (27 Oct):  Chance of Showers and Cool.  Snow level 3-4000 Feet.  42/55

Wed (28 Oct):  Mostly Cloudy.  Chance of Rain.  41/59

ODA Meteorologist
weather at oda.state.or.us