[willamette-fcst] Forecast - Tuesday, August 26th, 2008

Willamette Valley Ag/Burning Forecast willamette-fcst at listsmart.osl.state.or.us
Tue Aug 26 07:48:59 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: 
     Tuesday, August 26th, 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:
     An upper-level trough combined with daytime heating to
     trigger a few afternoon showers Monday...mainly over the
     north valley.  Skies cleared overnight, allowing
     temperatures to drop into the 40s and low 50s across most of
     Western Oregon.  Cool temperatures and the moist ground
     helped areas of fog to form...mainly in the southern
     Willamette Valley, near Eugene, and along the coast. 
     Visible satellite imagery showed only patchy low clouds over
     Western Oregon.

     The Salem sounding this morning showed more cooling, from
     the surface to about 7500 feet, with warming above 7500
     feet.  Low-level northeasterly winds, from just above the
     surface throught 3000 feet, were helping to dry out the air
     mass.   The ODA surface analysis showed high pressure
     centers over Western Oregon, Western Washington, and Eastern
     Oregon with very weak pressure gradients across the
     Willamette Valley.

     A flat ridge of high pressure will give northwesterly flow
     aloft to the region today.  Transport winds over the valley
     will turn northerly this afternoon, as a thermal trough
     attempts to build northward into SW Oregon.  The north winds
     will drop humidities to near 30% this afternoon, which will
     aid in the drying of damp fields.  The air aloft is still
     quite cool for late August, so even with ample sunshine
     today, afternoon temperatures will remain below normal...in
     the mid 70s.

     A weather system is forecast to move across Southern British
     Columbia tonight with the trailing edge of the cold front
     increasing the onshore flow across NW Oregon.  Some Drizzle
     or very light rain is possible along the North Oregon Coast
     and in the Northern Willamette Valley Wednesday morning, but
     skies should clear Wednesday afternoon, as high pressure
     rebuilds over the region.

Surface Winds:
     NW 3-6 this morning, N 5-15 this afternoon.
Transport Winds:
     NNE 5 this morning, N 10 this afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height today will be near 4500 feet.  Ventilation index 45.
High Temperature:
     Salem\'s high temperature today will be near 76.
Humidities:
     Relative humidity drops to 50% by 1pm.
     Minimum relative humidity will be near 32%.
Sunrise/Sunset:
     Salem sunset tonight: 7:59pm; sunrise tomorrow: 6:29am.

Extended Outlook:
     Flat ridging aloft will dry the air mass Thursday with
     transport winds likely turning northerly.  A stronger
     upper-level trough is forecast to approach the coastline
     Friday afternoon with the flow aloft becoming southwesterly.
     Transport winds and mixing heights could become favorable
     Friday afternoon for open burning of dry fields.

     The upper-level trough is forecast to move over the region
     Saturday with increasing onshore flow cooling valley
     temperatures back into the 70s.  Some morning drizzle is
     possible...especially along the coast.  The flow aloft is
     forecast to become northwesterly Sunday with surface and
     transport winds likely turning northerly and drying the air
     mass.  Weak southwesterly flow aloft is forecast for early
     next week with near-normal temperatures.

     All of the long-range models are indicating a possible
     burning opportunity, sometime between Tuesday and Thursday
     of next week, as the flow aloft becomes southwesterly and
     induces increasing onshore flow.

Tomorrow (27 Aug):  AM Clouds...Slight Chance Drizzle North.  Afternoon Clearing.  51/76

Thu (28 Aug):  Mostly Sunny and Warmer.  50/83

Fri (29 Aug):  Mostly Sunny.  Increasing High Clouds Late.  53/83

Sat (30 Aug):  Morning Clouds.  Afternoon Clearing and Cooler.  55/75

Sun (31 Aug):  Becoming Mostly Sunny.  49/76

Mon (01 Sep):  Mostly Sunny.  49/81

Tue (02 Sep):  Mostly Sunny.  50/83

ODA Meteorologist
weather at oda.state.or.us



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