[willamette-fcst] Forecast - Monday, March 1st, 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.

Issued: 
     Monday, March 1st, 2010 at 9:00am.

Burn Advisory:
     Recommended burn times for agricultural burning are from 10:00am to 4:00pm.
     Stack burning is not allowed.

Weather Discussion:
     A strong upper-level ridge of high pressure dried things out
     over the weekend, with the freezing level over western
     Oregon rising from around 5000 feet on Saturday to 10,000
     feet by Sunday afternoon.  A few showers lingered on
     Saturday, mainly from the coast range westward, with mostly
     sunny skies on Sunday lifting coastal temperatures into the
     mid 50s and Willamette Valley highs to near 60 degrees.

     The upper-level ridge axis had shifted to over eastern
     Oregon this morning, with increasing southerly flow aloft
     over western Oregon.  The air aloft is still very warm, with
     a nearly 11,000 foot freezing level, measured early this
     morning, over both Salem and Medford.  Satellite imagery
     showed considerable high clouds had advanced over the
     western two-thirds of both Washington and Oregon, ahead of a
     weakening offshore weather system.  That helped to limit fog
     formation in the valleys of western Oregon this morning,
     although some sections of the Willamette Valley had
     visibilities reduced to one-quarter of a mile by fog.

     Morning mimimums only dropped into the upper 30s and low 40s across the
     Willamette Valley.  Hillsboro dipped down to 38 degrees and Eugene bottomed
     out at 39. The mid-morning ODA surface analysis showed weak easterly
     pressure-gradients across all of Oregon.  The Willaemtte Valley is protected
     from easterly winds, except for near the western end of the Columbia Gorge,
     so surface winds were mostly calm across the valley.  Due to considerable
     low clouds and areas of fog, valley temperatures had only risen in the low
     to mid 40s.  However, Troutdale had warmed into the low 50s, due to better
     mixing of the air, via easterly outflow from the Gorge gusting to around 25 mph.

     Thickening high and mid-level clouds will filter the
     sunshine today across western Oregon, with continued light
     winds.  Temperatures aloft are warm enough to support valley
     highs climbing into the 60s this afternoon, but cloud-cover
     and poor mixing of the air mass will likely combine to prohibit
     valley temperatures from climbing out of the mid to upper 50s.

Surface Winds:
     Var 0-5 this morning, Var 3-8 this afternoon.
Transport Winds:
     SE 3 this morning, S 8 this afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height today will be near 1500 feet.  Ventilation index 12.
High Temperature:
     Salem\'s high temperature today will be near 58.
Humidities:
     Minimum relative humidity will be near 57%.
Sunrise/Sunset:
     Salem sunset tonight: 6:00pm; sunrise tomorrow: 6:48am.

Extended Outlook:
     Increasing southerly flow aloft will eventually bring rain
     onshore overnight, with rain at times and slightly cooler
     temperatures Tuesday. The snow level will drop to around
     5000 feet by Tuesday afternoon, with a few inches of new
     snow likely in higher regions of the Cascades.  The next
     weather system will head mainly into southern Oregon and
     northern California, on Wednesday, with only a chance of
     rain as far north as the Willamette Valley.  It has a little
     colder air aloft associated with it, so snow levels may drop
     as low as the Cascade passes.

     A chance of showers may linger into Thursday, with the next
     system, on Friday, will also encounter the split-flow
     pattern in the jet stream offshore and move mainly into
     California.  A ridge of high pressure may bring some dry
     weather back over the weekend.  The next weather system is
     forecast to take aim a little more at Oregon, instead of
     California, Sunday night and Monday, bringing more rain and
     mountain snow.

Tomorrow (02 Mar):  Rain Likely.  Snow Level Dropping to 5-6000 Feet.  45/55

Wed (03 Mar):  Mostly Cloudy.  Chance of Rain...Mainly South.  Snow Level 4000 Feet.  40/54

Thu (04 Mar):  Partly Sunny.  Slight Chance of Showers.  37/54

Fri (05 Mar):  Rain Likely South. Chance of Rain North.  Snow Level 4000 Feet.  39/54

Sat (06 Mar):  Mostly Cloudy.  Decreasing Chance of Showers.  Snow Level 4-5000 Feet.  37/55

Sun (07 Mar):  Mostly Cloudy.  37/56

Mon (08 Mar):  Rain Likely.  Snow Level 4000 Feet.  40/53

ODA Meteorologist
weather at oda.state.or.us