[willamette-fcst] Willamette Valley Field Burning Forecast

Tue Sep 2 08:43:30 PDT 2014

SILVERTON HILLS FIELD BURNING FORECAST

OREGON DEPARTMENT OF FORESTRY WEATHER OFFICE

8:45 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. Skies are partly to mostly cloudy this morning with marine low clouds mostly along the east side of the Willamette Valley. Morning sounding shows low level wind flow from the NNW to NNE at 5 - 15 mph up to 4000 ft, and NW'erly above. Surface high pressure is to the north with favorable pressure gradients at +2.2 mb from Newport to Salem and +1.2 mb from Salem to Redmond.

Upper level trough will continue to drop southward over the state today. Marine low clouds will dissipate this morning but clouds will increase this afternoon as the trough and cold front move in. Moisture, if any, will not likely begin until this evening. This 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:

Clearing this morning with increasing clouds this afternoon.

Salem's high temperature today will be near 77 degrees (average is 80).

Relative humidity: Will drop below 60 percent around 11 a.m. drop to near 40 percent around 4 p.m.

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

Transport winds: N at 5 - 12 mph this morning 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 northerly tomorrow and offshore 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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