[willamette-fcst] Forecast - Monday, August 31st, 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: 
     Monday, August 31st, 2009 at 9:00am.

Burn Advisory:
     Agricultural burning is allowed.  Suggested burn times are from 12:00pm until 7:00pm.
     Preparatory burning is allowed from 12:00pm until 2:00pm with a 50 acre limit.
     Propane flaming is allowed from 12:00pm until 5:00pm.
     Stack burning is not allowed.

Weather Discussion:
     The upper-level trough that brought showers to the region
     late last week, and over the weekend, will continue to bring
     showers and thudnerstorms to much of central and eastern
     Idaho today. The next system is still a ways upstream and
     was dropping southeastward, from the Gulf of Alaska, off the
     British Columbia coastline.  Inbetween the two, Oregon and
     Washington will have fair weather today.

     Visible satellite imagery showed low clouds covering much of
     the coastline this morning, with patchy low clouds in the
     Willamette Valley...especially from Salem north. Skies were
     mostly clear over southwestern Oregon and areas east of the
     Cascades, with the exception of some clouds near the Idaho
     border in northeastern Oregon.  The ODA surface analysis
     showed a weak trough across central Washington...extending
     through central Oregon and into southwestern Oregon.  High
     pressure was nosing into western Washington with a weak
     north-northesterly flow across western Oregon.

     With a consierable northerly component to the low-level
     flow, skies should slowly clear along the coast later today,
     with mostly sunny skies expected across the Willamette
     Valley. Highs should climb into the mid to upper 60s along
     the coast and low to mid 80s in the Willamette Valley. 

     Forecast north-northeasterly transport winds may allow for
     limited open burning, in the extreme western portion of the
     south valley, later this morning. The transport winds are
     forecast to become almost due northerly this afternoon, which
     is not conducive to open burning in the Willamette Valley.

Surface Winds:
     N 5-10 this morning, NNW 7-15 this afternoon.
Transport Winds:
     N 10 this morning, N 13 this afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height today will be near 4000 feet.  Ventilation index 52.
High Temperature:
     Salem\'s high temperature today will be near 83.
Humidities:
     Relative humidity drops to 50% by 12pm.
     Minimum relative humidity will be near 38%.
Sunrise/Sunset:
     Salem sunset tonight: 7:50pm; sunrise tomorrow: 6:35am.

Extended Outlook:
     The Gulf of Alaska weather system is forecast to drops
     south-southeastward...staying well offshore Tuesday...slowly
     approaching the coastline Wednesday.  South-southwesterly
     flow aloft will increase over Washington and Oregon, with
     some increase in onshore flow at the surface.  That will
     likely cool valley temperature a couple of degrees and turn
     transport winds more westerly.  That may create an open
     burning opportunity Tuesday and/or Wednesday afternoon.

     That system is forecast to finally come onshore late
     Wedneday and early Thursday...bring a chance of showers to
     mainly western Washington and northwestern Oregon.  It
     appears that the best chance of showers in the Willamette
     Valley will be from about Salem north.  Some clearing is
     expected Thursday afternoon, as a transitory ridge moves
     over the region.

     The next system appears stronger and is forecast to come
     onshore Friday.  It appears likely that this system will be
     strong enough to bring showers to the entire Willamette
     Valley, but the timing of the onset of rain is still very
     much in question.  If the system comes onshore late enough,
     there could be burning opportunity, ahead of it, Friday
     afternoon.  A cool upper-level trough is forecast to swing
     onshore Satruday and Sunday, maintaining below normal
     temperatures and a chance of showers.  A dry northwesterly
     flow aloft is forecast for Labor Day.

Tomorrow (01 Sep):  Areas of AM Clouds.  Afternoon Sunshine.  55/81

Wed (02 Sep):  Areas of AM Clouds.  Afternoon Sunshine.  Chance of Showers Late.  54/81

Thu (03 Sep):  Chance of AM Showers...Mainly North.  Partly Cloudy in the Afternoon.  54/77

Fri (04 Sep):  Increasing Clouds.  Rain Likely by Evening.  53/77

Sat (05 Sep):  Mostly Cloudy and Cool.  Chance of Showers.  52/71

Sun (06 Sep):  Mostly Cloudy and Cool.  Chance of Showers.  51/72

Mon (07 Sep):  Becoming Mostly Sunny and Warmer in the Afternoon.  49/77

ODA Meteorologist
weather at oda.state.or.us