[willamette-fcst] Forecast - Wednesday, November 12th, 2008

[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: 
     Wednesday, November 12th, 2008 at 9:00am.

Burn Advisory:
     Agricultural burning is allowed.  Suggested burn times are from now until 3:00pm.
     Stack burning is not allowed.

Weather Discussion:
     The most active weather in the country is right here in the
     Pacific Northwest this morning, with a strong westerly jet
     stream continuing to send abundant moisture onshore into
     Washington and northern Oregon.  One-half to two-thirds of
     an inch of rain fell across the Willamette Valley Tuesday,
     as the first of two soaker-storms came onshore. Much greater
     amounts fell just to our north, with northwestern Washington
     getting 2-3 inches of rain.  The Oregon coast generally
     picked up from one and one-half to three inches of rain
     Tuesday.  Greater amounts fell in the coastal range and in
     the Cascades.  Timberline Lodge has received over three
     inches of rain in the past 24 hours.

     Oregon has been on the warm (south) side of the jet stream
     the past few days, with freezing levels staying above 6000
     feet.  The morning sounding from Salem showed continued
     warming aloft, with the freezing level near 11,000 feet. 
     Cascade pass temperatures were in the mid 40s this morning. 
     Early-month snows, at higher elevations, were rapidly
     melting this morning with only 12 inches remaining at the
     6000-foot elevation near Timberline Lodge.  Only trace
     amounts of snow remained along the roadside at Willamette
     Pass with no snow visible from the Santiam Pass roadside camera.

     Satellite imagery showed a solid band of clouds stretching
     from Montana and Wyoming westward across Idaho, Washington
     and Oregon.  Doppler radar continued to show moderate to
     heavy precipitation falling over much of western Washington
     with lighter rainfall over northern Oregon.  Dry conditions
     generally prevailed south and east of a line from The Dalles
     to Salem to Brookings, on the southern Oregon Coast.

     The ODA surface analysis showed an east-to-west oriented
     cold front pushing into northwestern Washington with strong
     southerly pressure gradients extending southward well into
     Oregon.  South winds were gusting to around 30 mph over much
     of the northern half of Oregon, on both sides of the
     Cascades.  South winds were bringing very mild conditions to
     most of the state with mid-morning temperatures near 60
     degrees from the coast, across the Willamette Valley, to the
     Columbia Basin of northeast Oregon.

     The cold front, to our north, is forecast to slowly sag
     southward today with rain expected to increase across
     northern and western Oregon this afternoon.  The moisture
     feed into the frontal zone will be decreasing, as the front
     moves south, but locally heavy rainfall is still likely
     later today and tonight across northwestern
     Oregon...especially over the coast range and the Cascades.

     Additional rainfall totals, in the Willamette Valley, will
     likely range from one-half to one inch, before the rain
     tapers off Thursday morning.  Greater amounts are likely
     along the coast and in the mountains.  Blustery southerly
     winds will slowly turn more westerly and decrease later
     today and tonight.  Temperatures will likely stay near 60
     degrees today and slowly cool overnight, in the wake of the
     cold front.

Surface Winds:
     S 10-20 G30 this morning, SSW 10-20 G30 this afternoon.
Transport Winds:
     SSW 35 this morning, SW 35 this afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height today will be near 1500 feet.  Ventilation index 53.
High Temperature:
     Salem\'s high temperature today will be near 60.
Humidities:
     Minimum relative humidity will be near 87%.
Sunrise/Sunset:
     Salem sunset tonight: 4:46pm; sunrise tomorrow: 7:08am.

Extended Outlook:
     A major change, to a drier weather pattern, is forecast by
     all of the computer models, beginning tomorrow.  A bulding
     upper-level ridge of high pressure, just off the west coast,
     will shut off the tropical moisture feed and turn the flow
     aloft northwesterly by Thursday afternoon.  Temperatures
     will remain above normal, but valley highs will likely stay
     below 60 degrees.  A little cooler air aloft should drop the
     freezing level to about 8000 feet.

     The upper-level ridge axis is forecast to move directly over
     Oregon Friday through Sunday.  The surface flow will turn
     offshore for further drying of the air mass. The freezing
     level will likely jump back over 10,000 feet, with low-level
     temperature inversions developing.  Easterly winds, from the
     Columbia Gorge, will help to clear morning fog from the
     north valley, but it could be fairly persistent in the south
     valley.  Temperatures will vary considerably, depending on
     the extent and duration of valley fog, from day to day.

     The ridge if foreast to weaken and shift far enough east to
     allow a weak cold front to mix out the low-level temperature
     inversion Monday and bring back a chance of rain.  Another
     ridge is forecast to dry things back out Tuesday and
     Wednesday with offshore flow re-developing.

Tomorrow (13 Nov):  Rain Tapering off with Partial Afternoon Clearing. 53/57

Fri (14 Nov):  Morning Fog.  Afternoon Clearing...Mainly North.  40/55

Sat (15 Nov):  Morning Fog.  Afternoon Clearing...Mainly North.  42/56

Sun (16 Nov):  Morning Fog.  Afternoon Clearing...Mainly North.  42/57

Mon (17 Nov):  Increasing Clouds.  Chance of Light Rain Late.  44/57

Tue (18 Nov):  Rain Ending Early.  Becoming Partly Cloudy.  41/53

Wed (19 Nov):  Mostly Sunny.   35/51

ODA Meteorologist
weather at oda.state.or.us