[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.

Issued: 
     Friday, March 6th, 2009 at 9:00am.

Burn Advisory:
     Agricultural burning is allowed.  Suggested burn times are from 9:00am until 4:00pm.
     Straw stack burning is allowed from 9:00am until 4:00pm.

Weather Discussion:
     Showers ended overnight, and skies slowly cleared, across
     northwestern Oregon, as a modified Arctic cold front pushed
     south across the northern half of Oregon.  Rainfall amounts
     in the past 24-hours, ending at 4am, were generally between
     one-tenth and one-quarter of an inch across 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.

     The weakening cold front was draped across the middle of
     Oregon, at mid morning, with mostly clear skies to the north
     and mostly cloudy skies, with a few light rain and snow
     showers, to the south.  Brookings had some light rain this
     morning with some light snow in Klamath Falls and flurries
     in Pendleton.  Doppler radar showed little in the way of
     shower activity, so any precipitation this morning should be
     quite light.  The ODA surface analysis showed very weak
     pressure gradients across western Oregon, with stronger
     northwesterly gradients across central and eastern Oregon.

     Light valley winds and clearing skies allowed temperatures
     to drop below freezing across much of the Willamette Valley
     this morning with areas of fog forming.  Aurora and
     McMinnville dipped down to 29 degrees.  Hillsboro dropped at
     least down to 30 degrees, with both Salem and Eugene
     dropping below freezing.  Corvallis also dipped to at least
     32 degrees.  In contrast, cloudy skies, ahead of the
     weakening Arctic front, held temperatures across
     southwestern Oregon in the mid to upper 30s.  Minimums east
     of the Cascades were mostly in the 20s, except for the
     higher elevations of northeast Oregon, where clearing skies
     allowed the temperature to drop down to 11 degrees at
     Meacham and 19 degrees at Baker City.

     A weak transitory upper-level ridge was ushering in a drier
     north-northwesterly flow aloft over Oregon this morning. 
     That will help to clear skies today, from northwest to
     southeast, across the state.  Some sunshine will help
     Willamette Valley temperatures recover to near 50 degrees
     this afternoon. The air mass is still very cold aloft, with
     the freezing levels over Salem and Medford measured at just
     2400 and 3300 feet respectively early this morning. That
     will combine wth daytime surface heating to lift mixing
     heights to near 4000 feet this afternoon.  Valley winds will
     be light this morning and weak northwesterly this afternoon.

     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:
     Var 0-5 this morning, NW 5 this afternoon.
Transport Winds:
     NNW 5 this morning, 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. 
     Temperatures will be well below normal with snow levels only
     lifting to about 1500 feet Monday afternoon. Partial
     clearing and a cold north-northwesterly flow aloft should
     allow much of the valley to drop well below freezing Monday night.

     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