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

     This daily Willamette Valley Agricultural Weather Forecast will become a seasonal product,
     as of Friday April 16th. The last broadcast and email of this forecast will be today at
     12:00 p.m. 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 9:00am.

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

Weather Discussion:
     
     An broad upper-level trough, centered about 350 miles off the Oregon coast, rotated a spoke
     of energy northward, across Oregon, Wednesday evening.  Plenty of daytime heating, ahead of
     that disturbance, added fuel to the showers, as they developed over the Cascades and
     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 mid-morning, Doppler radar showed the main rain bands had moved north of the state,
     with light rain being reported across much of western, south-central, and southeastern
     Washington.  A few areas of light rain also extended into northeastern Oregon.  Light
     rain was just ending over the extreme northern Willamette Valley and along the northern
     Oregon coast. In the wake of the shower activity, satellite imagery showed mostly sunny
     skies over most of Oregon at mid-morning, with a few areas of western valley fog. 
     Visibilites in Corvallis and Eugene were only around one-quarter of a mile due to fog.

     With cloudy and rainy conditions, overnight temperatures stayed in the 40s across western
     Oregon.  The mid-morning ODA surface analysis showed very weak pressure gradients
     over western Oregon.  Valley winds were mostly light southeasterly, and temperatures were
     in the mid to upper 40s.  No upper-level disturbances are forecast to rotate across Oregon
     today, so daytime heating will likely only generate isolated shower activity, at most, 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 mid 60s.

Surface Winds:
     SSE 3-7 this morning, NNW 3-8 this afternoon.
Transport Winds:
     SSE 5 this morning, 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:
     Relative humidity drops to 50% by 1pm.
     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 into the low 70s. The long-range models continue to show a strong cold front
     coming onshore by Monday afternoon...followed by a cool trough on Tuesday. More weak
     weather systems are slated to make their way onshore during the second half of next week,
     but they forecast to move mainly into Washington and southern British Columbia.

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.  46/72

Mon (19 Apr):  Rain Likely Developing. Cooler. Snow Level Dropping to 4-5000 Feet.  47/62

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.  39/61

Thu (22 Apr):  Becoming Partly Sunny. Chance of Showers North. Snow Level 4000 Feet.  39/60

ODA Meteorologist
weather at oda.state.or.us