[willamette-fcst] Willamette Valley Field Burning Forecast

Tue Sep 6 08:51:54 PDT 2016

SILVERTON HILLS FIELD BURNING FORECAST

OREGON DEPARTMENT OF FORESTRY WEATHER OFFICE

8:45 AM PDT TUE SEP 6, 2016

BURN ADVISORY:

Agricultural burning is allowed from 11:00 a.m to 5:30 p.m.

Prep burning is not allowed.

WEATHER DISCUSSION:

Minor front moved through the region earlier this morning bringing a few hundredths to about a tenth of an inch of rain. Radar shows that most of the rain has moved east of the region. Moist W to NW flow aloft will keep skies mostly cloudy with a chance of a few more showers today. Humidity is not expected to go below 60 percent. Pressure gradients are evenly stacked with +.4 from Newport to Salem as well as +.4 from Salem to Redmond. Cloudy skies and scattered showers will keep fields generally wet today.

TODAY'S FORECAST:

Cloudy with scattered light showers.

Salem's high temperature near 67 degrees (average is 80).

Relative humidity: Will drop to a low of about 60 - 65 percent around 5 p.m.

Surface winds: S at 8 - 13 mph this morning becoming to S to SW at 6 - 12 mph this afternoon.

Transport winds: S to SW at 12 - 20 mph, gradually diminishing this afternoon.

Mixing height: Rising to 3000 ft by 11 a.m., rising to near 5000 ft by 4 p.m.

Salem's sunset tonight: 7:39 p.m.

(Salem Airport data for Monday, Sep. 5: High 75°F; Rainfall: .00")

(Maximum Ventilation Index expected today: 100)

EXTENDED DISCUSSION:

Upper level weather pattern remains mostly unchanged through the week with NW'erly flow aloft. Gradually an upper level ridge builds over the eastern Pacific and the state later in the week. This will mean enough onshore flow to keep skies cloudy, although, not as cloudy today. A weak thermal trough will form along the coast on Friday and warm temperatures to around 80F. Wind flow will be NNW to N and bring marginal burning opportunities. A dry cold front is expected to move down from the north over the weekend, but wind flow will likely remain NW to N.

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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