[willamette-fcst] Forecast - Wednesday, July 29th, 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.

...State Fire Marshal Conditions will likely be met by early this afternoon...

Issued: 
     Wednesday, July 29th, 2009 at 8:40am.

Burn Advisory:
     Agricultural burning is not recommended.
     Preparatory burning is not allowed.
     Propane flaming is not allowed.
     Stack burning is not allowed.

Weather Discussion:
     Tuesday was a scorcher across all of western Oregon except
     for right along the immediate coastline.  Willamette Valley
     temperatures approached all-time record highs late Tuesday
     afternoon and easily soared past the daily records.  Salem
     hit 107 degrees and Portland peaked at 106, both missing
     their all-time record highs by just 1 degree.  Eugene,
     Aurora, and McMinnville also hit 106 degrees.  Roseburg,
     Medford, and The Dalles were the hot spots in the state with
     108 degrees.  The beaches were mostly in the 70s and 80s,
     but temperatures soared over 100 as far west as the coast
     range passes.  Central and eastern Oregon highs were mostly
     in the 90s and low 100s.

     Slightly drier air allowed temperatures to dip a couple of
     degrees lower than Tuesday morning across the northern
     Willamette Valley.  Portland dipped to 72 this morning,
     after tying the all-time record warm minimum Tuesday morning
     with 74.  Salem was also a touch cooler this morning with a
     low of 69, after tying the all-time record warm minimum of
     70 the past two mornings.  Minimums were mostly in the mid
     60s across the rest of the Willamette Valley.

     No major changes are forecast to the general weather pattern
     today, so one more ultra-hot day is in store, before a slow
     cooling trend begins. The surface thermal trough was well
     developed and extended northward from southwestern Oregon
     through western Washington.  The trough had moved just
     inland over western Oregon but continued to extend to the
     coastline in western Washington.

     Visible satellite imagery showed more extensive low clouds and
     fog along the Oregon coast this morning...stretching all the way
     north to the mouth of the Columbia River.  That will cool temperatures
     today along the immediate coastline, but sunny skies and very warm
     air aloft will combine to bring another record-breaking afternoon to
     the interior of western Oregon.  Willamette Valley temperatures
     should be within a degree or two of where they were on Tuesday.

     Like yesterday, State Fire Marshal conditions will likely be
     met across the Willamette Valley by early this afternoon,
     due to high temperatures and low relative humidity.  Also
     like yesterday, increasing northerly winds, in the
     afternoon, will add to the fire danger potential.

Surface Winds:
     Var 0-5 this morning, N 5-15 this afternoon.
Transport Winds:
     NE 4 this morning, NNW 8 this afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height today will be near 5500 feet.  Ventilation index 44.
High Temperature:
     Salem\'s high temperature today will be near 107.
Humidities:
     Minimum relative humidity will be near 20%.
Sunrise/Sunset:
     Salem sunset tonight: 8:42pm; sunrise tomorrow: 5:56am.

Extended Outlook:
     Some minor cooling is forecast for late Thursday, as the
     thermal trough begins shifting eastward.  Willamette Valley
     highs will back off to the 95-100 degree range.  Overnight
     minimums will also cool back into 60s and upper 50s...making
     it feel a little more confortable.  The upper-level ridge is
     forecast weaken some on Friday with increasing westerly flow
     aloft.  That should shift the surface thermal trough east of
     the Cascades and bring enough onshore flow into western Oregon
     to cool Willamette Valley highs back into the low to mid 90s.

     By the weekend, an approaching upper-level trough may
     increase the southerly flow aloft enough to introduce a
     chance of thunderstorms to most of the state.  That would be
     a typical scenario following an intense heat-wave.  The
     speed of the ultimate cool-down appears as if it will be
     gradual, with a little more marine air seeping into the
     western valleys each day.  Due to the forecast
     south-southeaseterly flow aloft, it is not clear whether or
     not this cool-down will create any burning opportunities.

Tomorrow (30 Jul):  Sunny and Hot.  66/100

Fri (31 Jul):  Sunny.  A Little Cooler with Weak Onshore Flow Developing.  64/95

Sat (01 Aug):  Partly Cloudy.  Muggy.  Chance of T-Storms.  62/93

Sun (02 Aug):  Mostly Cloudy.  Muggy.  Good Chance of T-Storms.  60/89

Mon (03 Aug):  Mostly Cloudy.  Chance of Showers or T-Storms.  Cooler.  57/86

Tue (04 Aug):  Mostly Cloudy.  Chance of Showers and T-Storms.  56/83

Wed (05 Aug):  Mostly Cloudy.  Chance of Showers and T-Storms.  55/83

ODA Meteorologist
weather at oda.state.or.us