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

Tue Sep 2 11:52:28 PDT 2014

SILVERTON HILLS FIELD BURNING FORECAST

OREGON DEPARTMENT OF FORESTRY WEATHER OFFICE

11:50 AM PDT TUE SEP 2, 2014

BURN ADVISORY:

Agricultural burning is not recommended.

Prep burning is not allowed.

WEATHER DISCUSSION:

Upper level trough is dropping over the state today from the northwest. The cold front is passing through the Puget Sound area currently. Skies are mostly clear with just a few scattered clouds. Surface high pressure has moved southward and is mainly west of the region. Due to lingering cloudiness in the valley gradients are stacked a little higher in the Cascades than the Coast Range now. Current gradients are +2.5 mb from Newport to Salem and +3.0 mb from Salem to Redmond.

Upper level trough will continue to drop southward over the state today with the cold front arriving during the late afternoon. Clouds will increase this afternoon but moisture is unlikely other than some sprinkles as the trough moves through this evening. The front will kick off a marine push with winds shifting from northerly this morning to NW'erly this afternoon. Mixing height will reach 3000 ft around noon and lift to 5000 ft by mid-afternoon.

TODAY'S FORECAST:

Mostly clear early with increasing clouds this afternoon.

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

Relative humidity: Will drop to near 40 percent around 4 p.m.

Surface winds: NW to N at 5 - 10 mph, increasing to WNW to NW at 8 - 15 mph this afternoon.

Transport winds: NNW to N at 5 - 12 mph, shifting to NW'erly at 10 - 20 mph this afternoon and evening.

Mixing height: Rising to 3000 ft around noon, rising above 5000 ft by 3 p.m.

Salem's sunset tonight: 7:47 p.m.

(Salem Airport data for Monday, Sept. 1: High 83°F; Rainfall: .00")

(Maximum Ventilation Index expected today: 75)

EXTENDED DISCUSSION:

Upper level ridge quickly moves in behind today's trough and cold front with clearing skies tomorrow and warming temperatures through the remainder of the week. Wind flow will turn from northwest to northerly tomorrow and northeasterly Thursday and Friday as the upper ridge builds in and a surface thermal trough moves up the coast. Burn opportunities will be marginal to unlikely after today.

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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