[willamette-fcst] Forecast - Friday, August 22nd, 2008

Willamette Valley Ag/Burning Forecast willamette-fcst at listsmart.osl.state.or.us
Fri Aug 22 07:59:46 PDT 2008




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: 
     Friday, August 22nd, 2008 at 9:00am.

Burn Advisory:
     Agricultural burning is allowed.  Suggested burn times are from 12:00pm until 7:00pm.
     Preparatory burning is not allowed.
     Propane flaming is not allowed.
     Stack burning is not allowed.

Weather Discussion:
     Showers tapered off early on Thursday across Western Oregon,
     with the flow aloft turning northwesterly, in the wake of a
     strong upper-level trough that brought soaking rains to the
     Willamette Valley Tuesday and Wednesday.  Rainfall amounts
     in the 24 hours ending at 5am today were generlaly less than
     one-tenth of an inch across the valley.  With some sunbreaks
     Thursday afternoon, valley high temperatures reached the low
     70s, after staying in the upper 60s Wednesday.  Relative
     humidties dropped below 50% Thursday afternoon in the
     valley, which aided the drying of damp fields.

     The ODA surface analysis showed high pressure centered over
     NE Oregon and a weak thermal low pressure trough building
     northward into Western Oregon.  Gradients were weak
     north-northeasterly across the Willamette Valley with
     surface winds light and variable at mid-morning.  Clearing
     skies overnight allowed temperatures to drop into the mid to
     upper 40s across much of the valley this morning with areas
     of ground fog.  Mid-morning temperatures had recovered into
     the mid to upper 50s.

     A flat upper-level ridge of high pressure was moving over
     the region this morning.  The Salem sounding showed
     considerable warming and drying aloft since Thursday
     morning.  Satellite imagery showed both low and mid-level
     clouds over the Willamette Valley with some breaks in the
     overcast.  Fields will get an opportunity to further dry out
     today, as the air mass continues to warm up and dry out. 
     Skies will become mostly sunny this afternoon with northerly
     winds and lower humidities.  Afternoon highs should reach 80
     degrees, which is about normal for late August.


Surface Winds:
     Var 3-8 this morning, N 5-15 this afternoon.
Transport Winds:
     NE 14 this morning, NNE 10 this afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height today will be near 4000 feet.  Ventilation index 56.
High Temperature:
     Salem\'s high temperature today will be near 80.
Humidities:
     Relative humidity drops to 50% by 1pm.
     Minimum relative humidity will be near 33%.
Sunrise/Sunset:
     Salem sunset tonight: 8:06pm; sunrise tomorrow: 6:24am.

Extended Outlook:
     The ridge will move over Montana Saturday, with increasing
     southwesterly flow aloft over Oregon.  Valley temperatures
     should warm into the mid 80s under mostly sunny skies.  The
     southwesterly flow aloft is forecast to further strengthen
     Sunday, as a broad upper-level trough in the Gulf of Alaska
     slowly shifts eastard.

     Rain from a fairly active cold front is forecast to move onto
     the Washington Coast Sunday afternoon and slowly sag south and
     east into the Willamette Valley Sunday night and Monday.  Rainfall
     totals from this system will likely range from one-tenth to
     one-quarter of an inch, with locally greater amounts, near the
     Cascade foothills, in the north.

     Showers will taper off Monday night with the flow aloft is
     becoming northwesterly.  The latest computer forecast
     guidance is suggesting that a building ridge of high
     pressure will shift the jet stream north into Southern
     British Columbia Tuesday through Friday, of next week, with
     dry and warmer weather returning to Oregon.  Surface winds
     are forecast to be mostly northerly.

Tomorrow (23 Aug):  Sunny and Warm.  52/85

Sun (24 Aug):  Increasing Clouds with a Chance of Rain Late.  54/82

Mon (25 Aug):  Rain Likely...Turning to Showers by Afternoon.  Much Cooler.  58/72

Tue (26 Aug):  Becoming Mostly Sunny.  49/76

Wed (27 Aug):  Sunny and Warmer.  49/81

Thu (28 Aug):  Sunny and Warm.  52/84

Fri (29 Aug):  Sunny and Warm.  54/84

ODA Meteorologist
weather at oda.state.or.us












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