[willamette-fcst] Silverton Hills AM Forecast_Gary.doc

[Willamette Valley Field Burning Forecast]

SILVERTON HILLS FIELD BURNING FORECAST

OREGON DEPARTMENT OF FORESTRY WEATHER OFFICE

8:55 AM PDT WED JUL 20, 2016


BURN ADVISORY:



Agricultural burning is not recommended.



Prep burning is not allowed.



WEATHER DISCUSSION:



An upper-level trough continues west of the Oregon coast and enough southwest flow is keeping marine clouds out of the valley today. Strong sunshine will allow for deep mixing today. Transport winds will be very light northerly this morning. The sunshine on both sides of the Cascades should cause the pressure gradients to becoming positively stacked and turn the transport wind northwest by late in the afternoon.



Salem's high temperature today will be near 83°F (average is 83°F).

Relative humidity:  Dropping below 60% by 10:00 a.m. and about 33% by 5:00 p.m.

Surface winds: N 2-4 mph becoming NW 6-9 mph after 5:00 p.m.

Transport winds: N 5-9 mph shifting to NW 7-10 mph by 5:00 p.m.

Mixing height: Rising to 3400 feet by 11:00 a.m. and then 5500 feet by 5:00 p.m.

Salem's sunset tonight: 8:51 p.m.



(Salem Airport data for Tuesday, July 19th: High 78°F; Rainfall: .00")

(Maximum Ventilation Index expected today: 55)



EXTENDED DISCUSSION:


A strong upper level low about 800 miles west-southwest of Coos Bay is moving towards the state and will pass over the valley by Thursday evening. Showers are possible late afternoon and into the evening with the winds turning westerly. A burning opportunity is possible on Thursday afternoon. Sunny and dry afternoons and near seasonal temperatures are expected by Friday and through the weekend. Burning conditions may be good again on Friday.



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



Gary Votaw

ODF Meteorologist

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