[willamette-fcst] Forecast - Friday, March 6th, 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.

...Next Update Not Scheduled Until Tuesday, March 10th at 9:00am...

NOON UPDATE

Issued: 
     Friday, March 6th, 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:
     A cold Arctic frontal system droppedsouth across Washington
     and into northern Oregon Thursday, producing between
     one-tenth and one-quarter of an inch across most of western
     Oregon.  Corvallis was one of the wettest locations with
     just over one-third of an inch.  Meanwhile, Medford was the
     dry spot with only a trace of rain.  Snow levels dropped to
     about 2000 feet with 6-12 inches of new snow reported at the
     ski resorts in the Cascades.

     Showers ended overnight, across northwestern Oregon, with
     slowly clearing skies allowing most Willamette Valley
     temperatures to drop below freezing early this morning. 
     Areas of fog also developed but quickly gave way to mostly
     sunny skies by later in the morning.  Hillsboro dipped to 28
     degrees early this morning.  Aurora and McMinnville followed
     close behind, both with minimums of 29.  Salem and Corvallis
     fell to 30 degrees and Eugene bottomed out at 31.  In
     contrast, cloudy skies, ahead of a weakening Arctic front,
     held temperatures across southwestern Oregon in the mid to
     upper 30s.  Medford only dropped to 36 degrees and Roseburg
     held up at 39.

     Morning minimums east of the Cascades were mostly in the
     20s, with widely scattered snow showers continuing into this
     morning.  Meacham, in the Blue Mountains, fell to 11
     degrees, and Baker City dipped into the upper teens.  The
     weakening cold front had pushed to about the southeast
     corner of Oregon by late this morning and extended back
     northwestward to about Tillamook.  Skies were parlty to
     mostly sunny north of the frontal zone but remained mostly
     cloudy to the south.  Doppler radar showed little in the way
     of shower activity, so any remaining shower activity, across
     southern and eastern Oregon, was light.

     The ODA surface analysis showed very weak pressure gradients
     across western Oregon, with stronger northwesterly gradients
     across central and eastern Oregon.  Brisk northwesterly
     winds were gusting to between 20 and 25 mph across the
     eastern third of the state.  Winds were light across western
     and central Oregon with light northerly winds across
     southern Oregon.

     A weak transitory upper-level ridge ushered in a drier
     north-northwesterly flow aloft over Oregon this morning. 
     That will continue to clear skies, from northwest to
     southeast, across the state this afternoon.  Moslty sunny
     skies had lifted Willamette valley temperatures into the mid
     40s by late this morning.  Cold air aloft will keep high
     temperatures from climbing much above 50 degrees this
     afternoon with surface heating creating some convective
     clouds, but the upper-level ridging preventing shower
     development. The freezing levels over Salem and Medford were
     measured at just 2400 and 3300 feet respectively early this morning.

     The break in the weather will be brief with clouds
     increasing across northwestern Oregon overnight, in response
     to a very cold system dropping southward along the British
     Columbia Coastline.  Willamette Valley temperatures should
     drop to near freezing tonight, due to the cold air mass over
     the region and light surface winds.  However, temperatures
     should warm above freezing Saturday morning, as the clouds
     begin to thicken and surface winds increase.

Surface Winds:
     NW 5 this afternoon.
Transport Winds:
     NNW 5 this afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height today will be near 4000 feet.  Ventilation index 20.
High Temperature:
     Salem\'s high temperature today will be near 50.
Humidities:
     Minimum relative humidity will be near 52%.
Sunrise/Sunset:
     Salem sunset tonight: 6:07pm; sunrise tomorrow: 6:39am.

Extended Outlook:
     The next weather system is forecast drop straight down the
     British Columbia Coastline and directly into Washington and
     Oregon. It will pull unseasonably cold air from the interior
     of British Columbia out over the warmer ocean waters and
     then back inland across Oregon, beginning Saturday afternoon
     and lasting into Monday.

     That forecast weather pattern is a perfect set-up for very
     low snow levels across western Washington and northwestern
     Oregon. Snow levels will likely start out near 2000 feet
     Saturday and drop to near the Willamette Valley floor
     Saturday night through Monday...especially in the overnight
     periods. Some accumulations of wet snow are possible, even
     at the lowest elevations, beginning Saturday night. Expect
     winter driving conditions over the coast range and Cascade
     passes, Saturday through Monday.

     Rain and snow showers should begin to taper off Monday night
     with gradually clearing skies across western Oregon.  An
     upper-level ridge is forecast to shift over the region
     Tuesday with a drier and cool northwestly flow aloft.  A
     weak warm front may bring some sprinkles and warming on
     Wednesday.  Thursday and perhaps Friday look dry and warmer,
     as a transitory upper-level ridge builds over the region.

Sat (07 Mar):  Rain By Late-Morning and Breezy...Turning to Rain/Snow Showers Late. 32/47

Sun (08 Mar):  Rain/Snow Showers.  Accumulating Wet Snow Possible on Valley Floors.  32/43

Mon (09 Mar):  Rain/Snow Showers.  Accumulating Wet Snow Possible on Valley Floors.  30/43

Tue (10 Mar):  A Frosty Morning...Partly Sunny and Cool.  28/47

Wed (11 Mar):  Chance of Sprinkles.  32/50

Thu (12 Mar):  Partly Cloudy and Warmer.  35/53

Fri (13 Mar):  Partly Cloudy and Warmer.  36/56

ODA Meteorologist
weather at oda.state.or.us