[willamette-fcst] Forecast - Tuesday, October 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: 
     Tuesday, October 6th, 2009 at 9:00am.

Burn Advisory:
     Agricultural burning is allowed.  Suggested burn times are from 1:00pm until 5:00pm.
     Propane flaming is allowed from 1:00pm until 5:00pm.
     Stack burning is not allowed.

Weather Discussion:
     A strong upper-level ridge of high pressure is building into
     the coastline with a dry north-northeasterly flow aloft over
     Washington and Oregon.  At the surface, a thermal trough is
     building northward, along the southern Oregon Coast, with a
     broad area of high pressure covering most of eastern
     Washington and eastern Oregon.  Light offshore flow dried
     out the low-level air mass across wesetern Oregon Monday
     afternoon and night.  Mostly clear skies allowed
     temperatures to drop into the low 30s across sections of the
     Willamette Valley by early this morning.  Eugene hit the
     freezing mark and McMinnville dipped to 33.  Hillsboro
     dropped down to at least 34 degrees and Salem fell to at
     least 37.

     With a drier air mass in place, valley fog is not nearly as
     extensive this morning across western Oregon.  Visible
     satellite imagery was showing some areas of fog, mainly in
     the southern Willamette Valley and in the valleys of
     southwestern Oregon.  Skies were mostly clear over the
     remainder of Oregon and virtually all of
     Washington...including along the coast.

     The Salem sounding this morning showed considerable warming
     aloft, with the frezing level jumping from 6800 feet Monday
     morning to 11,900 feet this morning.  Warmer air aloft will
     combine with more sunshine to lift afternoon temperatures
     into the 65-70 degree range across the Willamette Valley. 
     Winds will be light north-northeasterly this afternoon.

     A weak weather disturbance will slight southeastward, across
     southern British Columbia, tonight and into northern Idaho
     and Montana Wednesday.  That is forecast to turn the surface
     pressure gradients onshore...likely bringing some low
     clouds, and possible drizzle, onto the north coast.  Some
     low clouds should also make their way into mainly the
     northern Willamette Valley by Wednesday morning.  That
     should keep temperatures slightly warmer tonight in the
     north valley, but low to mid 30s are possible again tonight
     in the drier south valley.

Surface Winds:
     Var 0-7 this morning, NNE 5-12 this afternoon.
Transport Winds:
     NNE 5 this morning, NNE 7 this afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height today will be near 2700 feet.  Ventilation index 19.
High Temperature:
     Salem\'s high temperature today will be near 68.
Humidities:
     Relative humidity drops to 50% by 1pm.
     Minimum relative humidity will be near 39%.
Sunrise/Sunset:
     Salem sunset tonight: 6:43pm; sunrise tomorrow: 7:18am.

Extended Outlook:
     Cold weather systems are forecast to bring early-autumn
     snows to Montana Wednesday through Saturday, while Washington
     and Oregon stay under the influence of a dry and cool
     northerly flow aloft.  There will be areas of morning low
     clouds and fog but plenty of afternoon sunshine.  Highs will
     struggle to reach near-normal with continued chilly mornings.

     The upper-level ridge is forecast to build more directly
     over the west coast by late this weekend, with warmer air
     aloft and light offshore surface winds combining to possibly
     warm valley temperatures into the ow 70s Sunday and Monday. 
     The ridge is forecast to break down and shift east next
     week, with increasing westerly flow aloft opening the door
     for a series of Pacific storms to move onshore with
     widespread rains.

Tomorrow (07 Oct):  Areas of AM Low Clouds or Fog.  Mostly Sunny in the Afternoon.  40/66

Thu (08 Oct):  Areas of AM Fog.  A Few High Clouds in the Afternoon.  40/68

Fri (09 Oct):  Mostly Sunny.  39/68

Sat (10 Oct):  Mostly Sunny.  38/69

Sun (11 Oct):  Patchy AM Fog...Sunny and Mild in the Afternoon.  39/71

Mon (12 Oct):  Increasing Clouds Late.  43/70

Tue (13 Oct):  Rain Likely.  47/63

ODA Meteorologist
weather at oda.state.or.us