[willamette-fcst] fbs0719p.docx

Willamette Valley Field Burning Forecast willamette-fcst at listsmart.osl.state.or.us
Tue Jul 19 11:58:02 PDT 2016


SILVERTON HILLS FIELD BURNING FORECAST

OREGON DEPARTMENT OF FORESTRY WEATHER OFFICE

11:50 AM PDT TUE JUL 19, 2016


BURN ADVISORY:



Agricultural burning is not recommended.



Prep burning is not allowed.



WEATHER DISCUSSION:



Though there is still a good chance that pressure gradients will go positive this afternoon, weather is shaping up to more like Monday in many ways. Current showers and thunderstorms may limit sunshine east of the Cascades while clouds are also thicker than expected in the Willamette Valley. Further monitoring will be required to assess burn opportunities.



An upper-level trough, centered just off the northern Oregon coast continues to cause cool, moist, and somewhat unstable and SW flow aloft over Oregon. The deep marine layer will keep skies mostly cloudy this afternoon but also allow for excellent mixing with light SW transport winds turning W by late afternoon.



Salem's high temperature today will be near 75°F (average is 83°F).

Relative humidity:  Dropping to around 50% by 2:00 p.m.

Surface winds: SSW 3 mph increasing 6-9 mph during the afternoon then W 6-8 mph by 5:00 p.m.

Transport winds: SW 8-10 mph shifting to W by 5:00 p.m.

Mixing height: Rising to 5000 feet by 2:00 p.m.

Salem's sunset tonight: 8:52 p.m.



(Salem Airport data for Monday, July 18th: High 76°F; Rainfall: .00")

(Maximum Ventilation Index expected today: 50)



EXTENDED DISCUSSION:


Conditions on Wednesday will be similar though with a little higher chance of showers. The upper level trough is expected to move across Oregon and Washington on Thursday night and Friday. Mostly cloudy skies, onshore flow and good mixing heights will persist through Friday with somewhat more sun in the afternoons. Then sunnier and warmer for the weekend.



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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