[willamette-fcst] Forecast - Monday, April 5th, 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.

NOON UPDATE

Issued: 
     Monday, April 5th, 2010 at 12:00pm.

Burn Advisory:
     Recommended burn times for agricultural burning are from now until 5:30pm.
     Straw stack burning is allowed from now until 5:00pm.

Weather Discussion:
     A cold upper level trough was centered just offshore as of late
     this morning. Satellite imagery showed an enhanced area of clouds
     arcing around a circulation center, about 150 miles off the
     northern Oregon coast, and into western Oregon.  Doppler
     radar showed several bands of showers rotating onshore
     and across western Oregon.  The bulk of the showers were north
     and west of a Portland-to-McMinnville-to-Newport line and
     moving quickly to the north-northeast, in a brisk
     south-southwesterly flow aloft.

     The late-morning ODA surface analysis showed southerly
     pressure gradients continuing to tighten across western
     Oregon, in association with the approaching upper-level
     disturbance.  South winds were gusting to around 30 mph,
     from McMinnville to Eugene.  Even with the gusty southerly
     winds, surface temperatures had mostly only warmed into the
     mid 40s across western Oregon.  Just ahead of the
     upper-level disturbance, some sunbreaks helped Cascade pass
     temperatures lift above freezing.  However, the air mass
     aloft is still quite cold, so pass temperatures should
     quickly fall back below freezing this afternoon, as showers
     increase with more snow accumulations likely.

     As the offshore upper-level disturbance slowly advances
     eastward, this afternoon, so will the showers and blustery
     southerly winds.  Cool, showery, and blustery weather will
     sweep across all of western Oregon this afternoon.  There is
     even a chance of a thunderstorms and/or bursts of small
     hail.  A few inches of additional snow are likely
     over the Cascades and higher elevations of the coast range. 
     High temperatures will be about 10 degrees below normal. 
     Salem\'s normal high temperature today is 60 degrees.

     Shower activity will begin to decrease this evening, as the
     flow aloft slowly turns more northwesterly.  The bulk of the
     showers will hang out over the western (windward) slopes of
     the coast range and the Cascades.  Southerly winds will also
     slowly decrease overnight but should stay strong enough to
     keep the atmosphere well-mixed and keep surface temperatures
     from dropping much below the upper 30s.

Surface Winds:
     S 12-25 G35 this afternoon.
Transport Winds:
     SSW 35 this afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height today will be near 4000 feet.  Ventilation index 140.
High Temperature:
     Salem\'s high temperature today will be near 49.
Humidities:
     Minimum relative humidity will be near 65%.
Sunrise/Sunset:
     Salem sunset tonight: 7:45pm; sunrise tomorrow: 6:44am.

Extended Outlook:
     Showers will continue to taper off Tuesday, as the
     northwesterly flow aloft begins to dry out.  Wednesday looks
     dry and warmer, with the possible exception of a weak warm
     front bringing some light rain to extreme northwestern
     Oregon Wednesday morning.  Temperatures could recover to
     near normal Wednesday afternoon, as skies continue to clear.      

     The break in the weather will be brief, with another strong
     cold front forecast to come onshore early Thursday.  An
     upper-level trough will keep a chance of showers over the
     region at least through Sunday, with continued fairly low
     snow levels.  Temperatures may warm close to normal on
     Wednesday but otherwise remain below normal for the extended
     forecast period.

Tomorrow (06 Apr):  Decreasing Showers.  Snow Level Rising to 3000 Feet.  37/53

Wed (07 Apr):  Becoming Partly Sunny and Warmer.  37/61

Thu (08 Apr):  Rain Likely with Mountain Snow.  Snow Level Dropping to 3000 Feet.  40/52

Fri (09 Apr):  Partly Cloudy.  Chance of Showers.  Snow Level 3-4000 Feet.  34/54

Sat (10 Apr):  Partly Cloudy.  Chance of Showers.  Snow Level 3-4000 Feet.  35/56

Sun (11 Apr):  Partly Cloudy.  Chance of Showers.  Snow Level 4000 Feet.  37/58

Mon (12 Apr):  Partly Cloudy.  Chance of Showers.  Snow Level 4000 Feet.  37/59

ODA Meteorologist
weather at oda.state.or.us