[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 JUL 28, 2014



BURN ADVISORY:



Agricultural burning is not recommended.

Prep burning is not allowed.



WEATHER DISCUSSION:



Upper level ridge extends over the state with axis over Idaho. Current pressure gradients are +2.5 mb from Newport to Salem and 0.0 mb from Salem to Redmond. Temperatures are running about 4 to 5 degrees above yesterday's readings. Wind flow this morning has been mostly N to NE at 5 - 8 mph.



Little change today with the high pressure ridge remaining anchored in place to the east. With weak southerly flow aloft, some thunderstorms will possibly develop east of the Cascade crest and limit much gradient stacking from Salem to Redmond during the afternoon hours. In general, expect mostly northerly flow through the day with just a minor marine influx this evening. Skies will remain clear and temperatures fairly hot, getting into the low 90s.



TODAY'S FORECAST:



Clear and very warm.



Salem's high temperature today will be near 93 degrees (average is 84).

Relative humidity: Dropping to 25 - 28 percent around 4 p.m.

Surface winds: Northerly at 6 - 12 mph this afternoon, NW to NNW this evening.

Transport winds: Mostly northerly at 8 - 15 mph this afternoon.

Mixing height: Rising to near 2500 ft by 1 p.m. and to 3000 - 3500 ft by 5 p.m.

Salem's sunset tonight: 8:43 p.m.



(Salem Airport data for Sunday, July 27th: High 88°F; Rainfall: .00")

(Maximum Ventilation Index expected today: 42)



EXTENDED DISCUSSION:



Little change in the upper level ridge pattern through the week with maybe a slightly weakening of the ridge and a little more NW to NNW flow during the late afternoon to evening hours. Expect very summerlike conditions with high temperatures reaching near 90 throughout the week. Thunderstorms are likely to increase over the Cascades and through eastern Oregon. Expect at best marginal burning conditions.



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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