[willamette-fcst] Forecast - Tuesday, March 24th, 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: 
     Tuesday, March 24th, 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:
     Rain spread onto the coast Monday morning and into the
     Willamette Valley Monday afternoon.  Showers continued
     overnight.  Total rainfall amounts ranged from one-tenth to
     near one-half inch of rain along the coast and from a few
     hundredths to almost one-quarter of an inch in the
     Willamette Valley.  Upsloping westerly flow aloft produced
     greater amounts of precipitation in the mountains.  The snow
     level started near 1000 feet Monday morning and stayed below
     3000 feet through Monday evening.  By this morning,
     continued westerly flow aloft had lifted the freezing levels
     over Salem and Medford to 4400 and 4700 feet respectively. 
     That puts the snow level this morning between 3000 and 3500 feet.

     ODOT road reports and cameras show snow-packed road surfaces
     over the Cascade passes this morning with snow continuing to
     fall and pass temperatures in the upper 20s.  Temperatures
     aloft were just warm enough for the coastal passes to get
     plain old rain.  Cloudy skies and areas of drizzle and/or
     very light rain were continuing in the Willamette Valley. 
     The clouds held temperatures mostly in the low 40s overnight
     through mid-morning.  Satellite imagery showed cloudy skies
     stretching across Washington, Oregon, and most of Idaho. 
     Doppler radar showed decreasing precipitation over western
     Oregon with some light rain and snow also making it across
     mainly the northern half of central and eastern Oregon.

     The ODA surface analysis indicated that a weakening frontal
     zone was pushing across western Washington and western
     Oregon at mid-morning.  Pressure gradients were southerly in
     the Willamette Valley and turned more westerly along the
     coast.  Weak pressure gradients were generating light winds
     east of the Cascades.  Western Oregon temperatures were in
     the 40-45 degree range.  Temperatures across central and
     eastern Oregon were elevation dependent and mostly in the
     30s.  Light snow was being reported in John Day and at
     Meacham.  Pendleton was seeing some light rain, but they
     were also the warm spot eastside with 40 degrees.

     5 inches of new snow fell overnight at Timberline Lodge and
     Mt. Hood Meadows.  Mt Bachelor picked up 3 inches of new
     snow.  The frontal zone will continue to weaken as it pushes
     east of the Cascades this afternoon.  Snow levels will
     remain in the 3-4000 foot range.  Another 1-4 inches of snow
     are possible, over the Cascade passes, before the snow
     tapers off later this afternoon.  Areas of light rain this
     morning will give way to a few light showers this afternoon
     across western Oregon.  Skies should reamin mostly cloudy,
     but slightly warmer air aloft will help valley temperatures
     climb into the low 50s this afternoon.  Highs on Monday were
     only in the mid to upper 40s.

Surface Winds:
     S 5-15 this morning, SW 5-15 this afternoon.
Transport Winds:
     SSW 15 this morning, SW 15 this afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height today will be near 2400 feet.  Ventilation index 36.
High Temperature:
     Salem\'s high temperature today will be near 52.
Humidities:
     Minimum relative humidity will be near 69%.
Sunrise/Sunset:
     Salem sunset tonight: 7:30pm; sunrise tomorrow: 7:05am.

Extended Outlook:
     A fast moving northwesterly jet stream will direct a
     stronger weather system southward into the region Wednesday.
      valley rain and mountain snow will increase, from northwest
     to southeast, across the state during the day.  Colder air
     aloft will lower to snow level to between 2500 and 3000
     feet, with up to a foot of new snow possible in the
     Cascades.  Due to the potential for heavy snow and strong
     winds, the National Weather Service has issued a Winter
     Storm Watch for the cascades valid from late tonight through
     Wednesday afternoon.  Rainfall amounts in the valley
     Wednesday should be around one-quarter of an inch with the
     greatest amounts in the north.

     A transitory ridge is forecast to bring dry and slightly
     warmer weather Thursday. A weak system is forecast to brush
     across Washington, and perhaps as far south as northern
     Oregon, on Friday.  A stronger system is forecast to drop
     further south, into the region, in a cool northwesterly flow
     aloft Saturday.  After some weak ridging Sunday, another
     system may drop into the region early next week.

Tomorrow (25 Mar):  Rain Likely.  Snow Level Dropping to 2500-3000 Feet.  40/50

Thu (26 Mar):  Becoming Partly Sunny.  Snow Level Rising to 4-5000 feet.  34/54

Fri (27 Mar):  Slight Chance of Rain...Mainly North.  Warmer.  Snow Level 5000 Feet.  36/59

Sat (28 Mar):  Chance of Rain...Mainly North. Snow Level 4-5000 Feet.  39/56

Sun (29 Mar):  Slight Chance of Showers...Mainly North.  Snow Level 5000 Feet.  39/57

Mon (30 Mar):  Increasing Chance of Rain and Mountain Snow.  Snow Level 4-5000 Feet.  37/55

Tue (31 Mar):  Showers Ending Early.  Partly Sunny in the Afternoon.  39/57

ODA Meteorologist
weather at oda.state.or.us