[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 AUG 25, 2014



BURN ADVISORY:



Fire Marshal conditions are possible this afternoon due to humidity's below 30 percent and wind gusts exceeding 15 mph.



Agricultural burning is not recommended.

Prep burning is not allowed.



WEATHER DISCUSSION:



Upper level ridge is nosing into the state today as a trough exits to the east. Skies are clear over the area with marine low clouds dissipating and moving away from the coast. Morning surface chart shows high pressure to the north with the thermal trough building up from the south. Current pressure gradients are +1.4 mb from Newport to Salem and -2.0 mb from Salem to Redmond.



Upper level ridge will gradually move into the region today bringing northerly flow and warmer temperatures. Mixing will lift above 5000 ft by 2 p.m. Surface pressure pattern remains on track with high pressure remaining to the north and the thermal trough building northward. This will likely keep gradients negatively stacked and not make for good burning conditions.

TODAY'S FORECAST:



Sunny and very warm.



Salem's high temperature today will be near 89 degrees (average is 81).

Relative humidity: Will drop below 30 percent by 3 p.m.

Surface winds: N to NNE at 10 - 18 mph this afternoon.

Transport winds: N to NNE at 13 - 18 mph this afternoon and evening.

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

Salem's sunset tonight: 8:01 p.m.



(Salem Airport data for Sunday, Aug 24th: High 85°F; Rainfall: .00")

(Maximum Ventilation Index expected today: 100+)



EXTENDED DISCUSSION:



Upper level ridge builds over the state on Tuesday then flattens and remains in place until the end of the week. Expect clear skies and fairly hot afternoon temperatures, reaching into the low to mid-90s. Low-level wind flow will likely remain northerly through Thursday with maybe a weak influx of marine air during the early evening hours. Burn opportunities look limited until Friday when a trough approaches and potentially brings a marine push Friday afternoon.



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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