[willamette-fcst] Forecast - Thursday, April 15th, 2010

Thu Apr 15 12:16:49 PDT 2010

Daily Smoke Management Forecast

Oregon Department of Agriculture
Smoke Management Program
Weather Outlook and Field Burning Advisory for Willamette Valley Growers and Fire Districts.

     This daily Willamette Valley Agricultural Weather Forecast will become a seasonal product,
     as of Friday April 16th. This is the last broadcast and email of this forecast. It will
     return as the \"Willamette Valley Field Burning Weather Forecast,\" issued daily via email
     and broadcast on WPOZ 585, beginning Thursday July 1st, 2010.

Issued: 
     Thursday, April 15th, 2010 at 12:00 p.m.

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

Weather Discussion:     
     A broad upper-level trough, centered well off the Oregon coast, rotated a spoke of energy
     northward, across Oregon, Wednesday evening.  Ahead of it, sunny skies provided enough
     afternoon heating to add fuel to the showers, as they developed over the Cascades.  The
     showers eventually rolled over the Willamette Valley, via a southeasterly flow aloft.

     CoCoRaHS reporting stations showed a broad range of rainfall totals across western Oregon
     Wednesday. Around one-quarter of an inch fell over most of southwestern Oregon, with the
     showers gaining intensity as they moved north, into Lane County, Wednesday evening.  Up
     to one-half inch of rain fell along the western slopes of the Lane County Cascades.  The
     rainfall totals ramped up to three-quarters of an inch, further north, in the Cascade
     foothills of Linn County and to more than an inch in the foothills of Marion County.  The
     snow level through of this was around 4500 feet, so the Cascade passes stayed mostly wet,
     but the ski areas reported up to one-half foot of new snow.

     The main area of showers turned to the northwest Wednesday night and moved out over the
     Willamette Valley.  Much of Marion and eastern Polk County picked up heavy rain, with
     valley totals over three-quarters of an inch.  The Salem Airport picked up .83 inches.
     Rainfall began to taper off, as the showers progressed northward overnight, but the
     northern Willamette Valle still picked up between one-quarter and one-half inch.  The
     southwestern Willamette Valley missed out on the heaviest rain but still picked up
     between one-tenth and one-quarter of an inch.

     By late this morning, Doppler radar showed the main rain bands had moved well north of
     Oregon and stretched from northwestern to southeastern Washington.  In the wake of the
     shower activity, satellite imagery showed mostly sunny skies over all but the extreme
     northwest corner of Oregon.

     The late-morning ODA surface analysis showed very weak northerly pressure gradients
     over western Oregon.  Valley winds were mostly around 5 mph or less and temperatures had
     warmed into the low to mid 50s.  No upper-level disturbances are forecast to rotate across
     Oregon today, so daytime heating will, at most, only generate isolated shower activity this
     afternoon and evening...mainly over the Cascades.  Southerly flow aloft will lift freezing
     levels to around 7000 feet this afternoon with mostly sunny skies helping valley
     temperatures climb into the low to mid 60s.

Surface Winds:
     NNW 3-8 this afternoon.
Transport Winds:
     NNW 8 this afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height today will be near 5000 feet.  Ventilation index 40.
High Temperature:
     Salem\'s high temperature today will be near 66.
Humidities:
     Minimum relative humidity will be near 40%.
Sunrise/Sunset:
     Salem sunset tonight: 7:58pm; sunrise tomorrow: 6:26am.

Extended Outlook:
     The next upper-level disturbance is forecast to be much weaker than the one that rolled
     through the region last night but will likely combine with daytime heating to trigger some
     showers across western Oregon Friday afternoon and evening. The entire upper-level trough
     is forecast to weaken and come onshore Saturday, but there may not be much strength left
     to it by that time.

     It still appears that Sunday will be the warmest day of the next week, with highs possibly
     climbing to near 70 degrees. The long-range models continue to show a strong cold front
     coming onshore by Monday afternoon...followed by a cool trough on Tuesday. More weather
     systems are slated to make their way onshore during the second half of next week, mainly
     into Washington and southern British Columbia, with a cool west-northwesterly flow aloft.
     A stronger system may come onshore about next Friday that could drop snow levels below the
     Cascade passes.

Tomorrow (16 Apr):  Chance of Mainly PM Showers.  Snow Level 6000 Feet.  41/68

Sat (17 Apr):  Mostly Cloudy.  Chance of Showers. Snow Level 6000 Feet. 44/64

Sun (18 Apr):  Partly Cloudy and Warm.  45/70

Mon (19 Apr):  Rain Likely Developing. Cooler. Snow Level Dropping to 4-5000 Feet.  47/60

Tue (20 Apr):  Showers Likely...Mainly South.  Snow Level 4000 Feet.  41/57

Wed (21 Apr):  Mostly Cloudy. Chance of Showers...Mainly North. Snow Level 5000 Feet.  37/59

Thu (22 Apr):  Mostly Cloudy. Chance of Showers...Mainly North. Snow Level 4000 Feet.  37/59

ODA Meteorologist
weather at oda.state.or.us