[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

11:40 AM PDT MON AUG 15, 2016



BURN ADVISORY:



Agricultural burning is not recommended.



Prep burning is allowed from now until 2 p.m. with a 50 acre limit.



WEATHER DISCUSSION:



Minor upper level ridge lies over the state today. Marine low clouds along the coast are burning off leaving the entire state cloud-free. Air mass is destabilizing due to full sunshine and rapidly warming temperatures. Expect good mixing this afternoon. Pressure gradients are evenly stacked this morning with +1.5 mb from Newport to Salem and +1.6 mb from Salem to Redmond. Gradients should remain near even or positively stacked throughout the day. Transport winds are northerly at 8 - 15 mph with surface winds northerly at 5 - 10 mph. Expect little change in wind direction except possibly turning NW'erly during the evening.



TODAY'S FORECAST:



Sunny and very warm.



Salem's high temperature today will be near 90 degrees (average is 82).

Relative humidity: Will reach a low near 30 percent around 5 p.m.

Surface winds: N at 7 - 15 mph.

Transport winds: N at 8 - 18 mph.

Mixing height: Rising to 4500 - 5000 ft by 4 p.m.

Salem's sunset tonight: 8:17 p.m.



(Salem Airport data for Sunday, July 14: High 94°F; Rainfall: .00")

(Maximum Ventilation Index expected today: 75)



EXTENDED DISCUSSION:



Upper level ridge will remain flat through early Wednesday then it will build over the eastern Pacific Thursday and Friday. Expect continued clear skies, very warm temperatures and northerly winds. As the ridge builds on Thursday the thermal trough will move up the coast, turn wind flow offshore and warm temperatures further, likely into the upper 90s. Given these conditions burn opportunities appear minimal 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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