[willamette-fcst] Willamette Valley Ag Weather Forecast

[Willamette Valley Ag/Burning Forecast]

Oregon Department of Agriculture
Smoke Management Program
Weather Outlook and Field Burning Advisory for Willamette 
Valley Growers and Fire Districts.

Issued:
      Thursday, February 26th, 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:
      A cold upper-level low-pressure system slowly sagged
      southward, along the Washington Coast, last night. 
 It
      circulated cold Arctic air, from southern British 
Columbia,
      over the warmer ocean waters and then inland across
      Washington and Oregon.  That increased the shower 
activity
      with progressively lowering snow levels.  By early 
this
      morning, wet snow showers were falling down to sea 
level
      along the Oregon coast and down to the floor of the
      Willamette Valley.

      Doppler radar showed the main area of snow showers 
extending
      from just south of Portland to near Corvallis and 
stretching
      from the coast to the creast of the Cascades. 
 Roadways were
      locally covered in slush along the I5 corridor with 
up to a
      couple of inches of snow reported on the eastern 
side of the
      valley near Stayton.  Several inches of snow fell 
over the
      coastal and Cascade passes with more than a foot of 
new snow
      reported at the ski areas on Mt. Hood.  More than 4 
feet of
      snow have fallen in the past 72 hours at Timberline 
Lodge.

      Winter Weather Advisories are in effect until noon 
today for
      northern and central Willamette Valley, north of 
Albany, for
      snow showers with local minor accumulations of wet 
snow.
      More significant snow accumulations are still 
possible in
      the coastal and Cascade passes.  As the upper-level
      low-pressure system moves east of the Cascades this
      afternoon, showers will should rapidly taper off 
across
      western Oregon with the snow level rising to about 
1500
      feet.  Willamette Valley temperatures should recover 
into
      the mid 40s this afternoon, after hovering near the 
freezing
      mark through mid-morning.

      The ODA surface analysis showed an Arcitc frontal 
boundary
      extending from just north of Seattle to near 
Spokane,
      Washington.  North of that line, temperatures were 
well
      below freezing with cold northerly winds.  The 
leading edge
      of the cold front that brought the low-elevation 
snow to
      Oregon was pushing into Idaho at mid-mornig. 
 Doppler radar
      showed to showers beginning to taper off across 
northwestern
      Oregon.  Winds were mostly southwesterly in the 
Willamette
      Valley between 5 and 15 mph.  Showers had ended 
along the
      coast, at Newport, where northwesterly winds were 
gusting to
      near 30 mph.  That is an indication that drier 
conditions
      will be moving into the interior valleys later this 
morning.

Surface Winds:
      WSW 5-15 G20 this morning, WSW 5-15 this afternoon.
Transport Winds:
      WSW 20 this morning, W 15 this afternoon.
Atmospheric Ventilation Conditions:
      Maximum mixing height today will be near 4000 feet. 
 Ventilation index 80.
High Temperature:
      Salem\'s high temperature today will be near 45.
Humidities:
      Minimum relative humidity will be near 55%.
Sunrise/Sunset:
      Salem sunset tonight: 5:56pm; sunrise tomorrow: 
6:53am.

Extended Outlook:
      The upper-level low-pressure system is forecast to 
move into
      Idaho tonight with showers ending and skies clearing 
across
      Oregon.  That will allow for much colder overnight
      temperatures.  Valley minimums will likely drop into 
the mid
      to upper 20s most areas.  Please be aware that wet 
road
      surfaces may freeze and create locally slick driving
      conditions through early Friday.  There may also be 
areas of
      morning fog.  A transitory ridge of high pressure 
will
      likely allow for at least partly sunny skies Friday, 
but
      temperatures will be well below normal.

      Mostly clear skies Friday evening will lead to areas 
of fog
      forming Friday night.  Valley temperatures should, 
once
      again, drop to near or below freezing by Saturday 
morning.
      The next weather system will increase clouds over 
the region
      Saturday with a chance of rain by the afternoon. 
 Increasing
      southwesterly flow aloft should lift the snow level 
to near
      or slighty above the Cascade passes.  Rain is likely
      Saturday night and Sunday, as the storm moves 
onshore.  Snow
      levels will hover around the Cascade passes Sunday, 
before
      dropping to near 3000 feet Sunday night.

      An upper-level trough will slowly move onshore 
Monday and
      Tuesday with an ongoing threat of showers.  That 
trough
      should not be nearly as cold as the one that came 
through
      the region this morning, so snow levels should stay 
in the
      3-4000 foot range.  Valley temperature will be near 
normal.
      A stronger and colder system is forecast to come 
onshore
      late Wednesday and Thursday.

Tomorrow (27 Feb):  Very Cold Start.  Partly Sunny and 
Cool Afternoon.  25/48

Sat (28 Feb):  Increasing Clouds.  Chance of PM Rain. 
 Snow Level Rising to 4000 Feet.  31/49

Sun (01 Mar):  Rain.  Snow Level 4000 Feet...Dropping to 
3000 Feet Late.  39/52

Mon (02 Mar):  Showers.  Snow Level  3-4000 Feet.  37/51

Tue (03 Mar):  Mostly Cloudy.  Chance of Showers.  Snow 
Level near 4000 Feet.  37/52

Wed (04 Mar):  Rain Increasing.  Snow Level 3-4000 Feet. 
 36/51

Thu (05 Mar):  Rain Turning to Showers.  Snow Level 
Dropping to 2000 feet.  35/49

ODA Meteorologist
weather at oda.state.or.us