[willamette-fcst] Forecast - Friday, February 27th, 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.

NOON UPDATE

Issued: 
     Friday, February 27th, 2009 at 12:00pm.

Burn Advisory:
     Agricultural burning is allowed.  Suggested burn times are from now until 4:00pm.
     Straw stack burning is allowed from now until 4:00pm.

Weather Discussion:
     The cold upper-level low-pressure system that moved across
     Oregon Thursday rapidly pushed east of the region
     overnight...allowing for clearing skies.  Willamette Valley
     temperatures dropped well below freezing overnight, with
     areas of dense fog making for locally slick travel conditions
     this morning.  McMinnville dipped down to just 26 degrees this
     morning, and it was only 27 in Hillsboro and 29 in Salem.

     Late-morning visible satellite imagery continued to show
     extensive low clouds covering much of western Oregon.  There
     were some sunbreaks along the coast and in the northern
     Willamette Valley, north of Salem.  Midday temperatures
     ranged from the cloudy mid 30s in Salem to the mid 40s along
     the coast and in the sunny Portland area.  The late-morning
     ODA surface analysis showed weak offshore (northeasterly)
     pressure gradients.  Winds were light north-northeasterly in
     the valley and easterly, gusting to 30 mph, at the western
     end of the Columbia Gorge.  The drier easterly flow helped
     to quickly clear the low clouds from the extreme north valley
     this morning.

     A transitory ridge of high pressure aloft and increasing
     offshore surface winds, should help to slowly clear the low
     clouds from the Willamette Valley this afternoon.  With a
     cold air mass still over the region (the morning freezing
     level was measured at just 1100 feet over Salem), and the
     persistent morning low clouds, high temperatures will
     struggle to hit the mid 40s in the central and south valley
     this afternoon, even with some sunbreaks.  With more
     sunshine, highs in the north valley may approach 50.

Surface Winds:
     NE 5 this afternoon.
Transport Winds:
     SE 5 this afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height today will be near 3000 feet.  Ventilation index 15.
High Temperature:
     Salem\'s high temperature today will be near 45.
Humidities:
     Minimum relative humidity will be near 68%.
Sunrise/Sunset:
     Salem sunset tonight: 5:57pm; sunrise tomorrow: 6:51am.

Extended Outlook:
     Mostly clear skies this evening will lead to areas of fog
     forming overnight, although increasing offshore flow should
     keep fog from forming across most of the north valley. 
     Valley temperatures should drop to below freezing in most
     areas by Saturday morning. The next weather system will
     increase clouds over the region Saturday, but dry offshore
     low-level flow will likely limit precipitation to just a few
     sprinkles.  Increasing southwesterly flow aloft should lift
     the snow levels slightly above the Cascade passes.

     The chance of rain will increase Saturday night, with rain
     likely by Sunday afternoon.  Strengthening southwesterly
     flow aloft should keep snow levels in the 5-6000 foot range,
     before they drop below pass levels Sunday night.  Willamette
     Valley temperatures may get rather balmy Sunday afternoon,
     ahead of the approaching storm system.  A slow-moving cold
     front is forecast to sweep rain and Mountain snow across
     Oregon Monday, with a cool upper-level trough continuing
     showers on Tuesday.  Showers should decrease Wednesday, with
     a stronger and colder system dropping into the region, from
     the Gulf of Alaska, Wednesday night.  A cold upper-level trough
     will bring showers, with very low snow levels, Thursday and Friday.

Sat (28 Feb):  Mostly Cloudy.  Slight Chance of Sprinkles.  Snow Level 6000 Feet.  30/50

Sun (01 Mar):  Increasing Chance of Rain.  Snow Level 5-6000 Feet...Dropping late.  39/57

Mon (02 Mar):  Rain at Times.  Snow Level  3-4000 Feet.  40/52

Tue (03 Mar):  Rain Turning to Showers.  Snow Level near 3-4000 Feet.  38/52

Wed (04 Mar):  Chance of Showers Early.  Rain Late.  Snow Level 3-4000 Feet.  36/51

Thu (05 Mar):  Rain & Windy...Turning to Showers.  Snow Level Dropping to 1500 feet.  38/49

Fri (06 Mar):  Showers and Cool.  Snow Level 500-1500 Feet.  33/47

ODA Meteorologist
weather at oda.state.or.us