[willamette-fcst] Forecast - Wednesday, March 25th, 2009

Wed Mar 25 09:09:17 PDT 2009

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, March 25th, 2009 at 9:00am.

Burn Advisory:
     Agricultural burning is allowed.  Suggested burn times are from now until 5:30pm.
     Straw stack burning is allowed from now until 5:30pm.

Weather Discussion:
     A vigorous upper-level trough dropped southward, into
     Washington and Oregon, overnight.  Satellite imagery showed
     cloudy skies covering both states this morning with surface
     and radar reports indicating widespread precipitation on
     both sides of the Cascades.  The mian jet stream energy is
     over and east of the Cascades.  The heaviest snow fell
     overnight in the Washington Cascades, where total snowfall
     amounts will be around 10-20 inches.  In the northern Oregon
     Cascades, Timberline Lodge received 8 inches of new snow
     overnight.  Lighter smounts extended further south, with Mt.
     Bachelor picking up 3 inches of new snow.

     Rainfall amounts west of the Cascades overnight ranged from
     just a few hundredths of an inch in the Willamette Valley to
     more than one-quarter of an inch along the north coast. 
     Light rain was continuing to fall along the coast and across
     the Willamette Valley this morning.  Snow was increasing in
     the Cascades with pass temperatures in the mid to upper 20s.

     Rain and mountain snow will continue for much of today and
     taper off this evening, as the upper-level disturbance
     slides into Idaho.  The snow level is about 3000 feet north
     and 4500 feet over southern Oregon.  Winter Storm Warnings
     are in effect for the northern Oregon Cascades for up to 15
     inches total snow accumulation from this storm.  Valley
     rainfall amounts could approach one-quarter of an inch.

     Cloudy skies held overnight temperatures in the low to mid
     40s west of the Cascades.  The ODA surface analysis showed
     southerly gradients across the Willamette Valley this
     morning, which should turn more westerly later today. 
     Afternoon temperatures will struggle to reach 50 degrees,
     due to clouds and light rain.  

Surface Winds:
     S 7-17 this morning, SW 7-17 this afternoon.
Transport Winds:
     SW 17 this morning, WNW 17 this afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height today will be near 3500 feet.  Ventilation index 60.
High Temperature:
     Salem\'s high temperature today will be near 50.
Humidities:
     Minimum relative humidity will be near 68%.
Sunrise/Sunset:
     Salem sunset tonight: 7:31pm; sunrise tomorrow: 7:03am.

Extended Outlook:
     A transitory ridge is forecast to build into the coastline
     Thursday, with conditions drying out across Oregon. A weak
     warm front will likely keep skies mostly cloudy.  It may be
     strong enough to produce some sprinkles, mainly along the
     coast and in the northern Willamette Valley, Thursday
     afternoon and night.  The jet stream is forecast to migrate
     slightly northward Friday, with skies staying mostly cloudy
     across Washington and extreme northern Oregon.  Some
     sprinkles are possible near the Washington border, with a
     few sunbreaks in the south valley.  The snow level will lift
     to around 5000 over northern Oregon and to 6-7000 feet over
     southern Oregon.  Willamette Valley temperatures will
     moderate to near, or even slightly above,
     normal...especially south.

     A vigorous cold front is forecast to swing onshore Saturday
     afternoon and night, with more rain, wind, and rapidly
     lowering snow levels.  Showers will taper off Sunday, as a
     transitory upper-level ridge moves over the region.  An
     active weather pattern is forcast for next week.  Another
     vigorous cold front is forecast to sweep across Washington
     and Oregon Monday with some drying Tuesday.  More storms are
     likely late Wednesday through Friday with snow levels
     dropping below the Cascade passes.

Thu (26 Mar):  Mostly Cloudy.  Chance of Sprinkles.  Snow Level Rising to 4-5000 feet.  37/54

Fri (27 Mar):  Chance of Sprinkles...Mainly North.  Warmer.  Snow Level 5-7000 Feet.  40/59

Sat (28 Mar):  Increasing Rain & Blustery. Snow Level Dropping to 2000 Feet Late.  42/53

Sun (29 Mar):  Showers Ending...Mostly Cloudy. Snow Level Lifting to 3500 Feet Late.  36/52

Mon (30 Mar):  Increasing Rain and Mountain Snow.  Snow Level Dropping to 2-3000 Feet.  37/50

Tue (31 Mar):  Showers Decreasing and Cool.  Snow Level 2-3000 feet.  34/53

Wed (01 Apr):  Mostly Cloudy.  Increasing Chance of Rain Late.  34/57

ODA Meteorologist
weather at oda.state.or.us