[willamette-fcst] Willamette Valley Field Burning Forecast - Noon Update

[Willamette Valley Field Burning Forecast]

SILVERTON HILLS FIELD BURNING FORECAST

OREGON DEPARTMENT OF FORESTRY WEATHER OFFICE

11:45 AM PDT MON SEP 12, 2016



BURN ADVISORY:



Agricultural burning is not recommended.



Prep burning is not allowed.



WEATHER DISCUSSION:



Upper level ridge is nosing into British Columbia this morning as this past weekend's dry trough is dropping southward. This weather pattern will leave the region under northeast flow both near the surface and aloft. Expect clear skies and breezy N to NE flow today. The thermal trough is moving up the coast today and will keep pressure gradients offshore, leaving little chance for burning.



TODAY'S FORECAST:



Sunny and warm.



Salem's high temperature near 80 degrees (average is 78).

Relative humidity: Will drop to near 25 percent around 5 p.m.

Surface winds: N to NE at 12 - 18 mph with gusts to 25 mph.

Transport winds: NNE to NE at 15 - 22 mph.

Mixing height: Rising above 5000 ft after 2 p.m.

Salem's sunset tonight: 7:27 p.m.



(Salem Airport data for Monday, Sep. 11: High 76°F; Rainfall: .00")

(Maximum Ventilation Index expected today: 125)



EXTENDED DISCUSSION:



Upper level ridge remains to the north through Tuesday with the trough to the south weakening and starting to move eastward. Expect continued offshore flow, clear skies and very warm temperatures. Ridge flattens on Wednesday and allows a cooling intrusion of SW to W marine air to move in during the afternoon. This day looks to be the best of the week for burning. Ridge rebuilds Thursday and Friday with wind flow turning back to northerly. No moisture is expected anytime this week.



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



Nick Yonker

ODF Meteorologist

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