[willamette-fcst] Silverton Hills AM Forecast_doug.doc

[Willamette Valley Field Burning Forecast]

SILVERTON HILLS FIELD BURNING FORECAST

OREGON DEPARTMENT OF FORESTRY WEATHER OFFICE

9:00 AM PDT FRI SEP 6, 2013



BURN ADVISORY:



Recommended times for agricultural burning are 1:00 p.m. to 5:30 p.m..

Prep burning is not allowed.



WEATHER DISCUSSION:



The upper level low is exiting the region today, leaving cool temperatures and south to southwest winds. After yesterday's flooding rains, fields will remain wet for several days. Expect scattered light showers and generally southwest to west winds today.



(Salem Airport data for Thurs., Sept. 5th: High 71°F; Rainfall 1.82")

(Maximum Ventilation Index expected today:  30)

TODAY'S FORECAST:



Cloudy with southwesterly surface winds and scattered light showers.



Salem's high temperature today will be around 70.

Relative humidity drops to 60-65% this afternoon.

Surface winds: S 10-15 mph, becoming SW-W 5-15 mph by afternoon.

Transport winds: SW 10-20.

Maximum mixing height: 2500 ft.

Sunset tonight: 7:39 p.m.



EXTENDED DISCUSSION:



Cloudy skies are also expected early on Saturday, but clearing should take over during the afternoon with mostly N winds and temperatures well up into the 70s. The drying trend will continue on Sunday accompanied by more warming.



For early next week, warm and dry conditions are expected to continue with highs potentially getting up into the 80s in the Silverton Hills.



The National Weather Service's digital forecast is available at:

http://forecast.weather.gov/MapClick.php?lat=44.90549606158295&lon=-122.8106689453125&site=pqr&unit=0&lg=en&FcstType=text



Notes:



     1.  Mixing height, as used here, is the lowest height at which the

         potential temperature exceeds the potential temperature at the

         surface.  As a practical matter it is the approximate height to

         which a smoke plume will rise assuming good ignition, dry fuels, and

         winds less than about 15mph.



     2.  Transport winds are a layer average through the mixing height,

         weighted slightly toward the winds at the top of the layer.



     3.  Ventilation Index is the height of the mixing layer times

         the transport wind speed divided by 1000.



     4.  Surface wind direction is the general expected wind direction.

         At a specific point surface winds are highly dependent on local

         terrain conditions.



This forecast is provided under an agreement between the Oregon Department of

Agriculture and the Oregon Department of Forestry.  For information contact ODA at 503-986-4701.



Doug Wesley

ODF Meteorologist


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