[willamette-fcst] Silverton Hills AM Forecast_Pete.doc

[Willamette Valley Field Burning Forecast]

SILVERTON HILLS FIELD BURNING FORECAST

OREGON DEPARTMENT OF FORESTRY WEATHER OFFICE

8:35 AM PDT MON AUG 22, 2016



BURN ADVISORY:



Agricultural burning is not recommended.



Prep burning is not allowed.



WEATHER DISCUSSION:



A dry marine push over the weekend brought an end to the recent heat-wave.  Temperatures will be close to average today under sunny skies.  Cool air aloft will provide excelling mixing, but negatively-stacked gradients and developing NNE transport winds will be unfavorable for burning.



TODAY'S FORECAST:



Sunny, mild, and a little breezy.



Salem's high temperature today will be near 79°F (average is 82°F).

Relative humidity:  Dropping to 50% around 11 a.m. and to near 35% by 5 p.m.

Surface winds: N 8-13 mph this morning; NNE 10-15 mph this afternoon.

Transport winds: NNE 10-15 mph.

Mixing height: Rising to 3000 feet around 11 a.m. and to 5000 feet by 5 p.m.

Salem's sunset tonight: 8:06 p.m.



(Salem Airport data for Sunday, August 21st: High 86°F; Rainfall: .00")

(Maximum Ventilation Index expected today: 75)



EXTENDED DISCUSSION:



The outlook for burning this week is bleak.  A building upper-level ridge, centered in the eastern Gulf of Alaska, will produce a dry northerly flow aloft over Oregon with increasing offshore transport winds and warming temperatures.  Valley highs should climb back into the 90s Wednesday through Friday with State Fire Marshal Conditions possible.  There is a chance of a marine push Friday afternoon, but that is likely to hold off until Saturday.



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 15 mph.



     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 (ft) times

         the transport wind speed (mph) 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 (ODA) and the Oregon Department of Forestry (ODF).  For

information contact ODA at 503-986-4701.



To add/remove your email address from this list, please go to:



http://listsmart.osl.state.or.us/mailman/listinfo/willamette-fcst



Pete Parsons

ODF Meteorologist
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