[willamette-fcst] Willamette Valley Field Burning Forecast

Mon Jul 13 08:43:51 PDT 2015

SILVERTON HILLS FIELD BURNING FORECAST

OREGON DEPARTMENT OF FORESTRY WEATHER OFFICE

8:45 AM PDT MON JUL 13, 2015

BURN ADVISORY:

Agricultural burning is not recommended.

Prep burning is not allowed.

WEATHER DISCUSSION:

Upper level trough has moved over the Pacific Northwest this morning and will remain in place through the day. Skies are mostly cloudy. Morning sounding shows a moist unstable layer up through 5000 ft. Surface wind flow has been showing a light SW to W at 3 - 5 mph. Otherwise, low-level winds up to 2500 ft have been light and variable and S to SSW at 5 - 10 mph above. Pressure gradients are +.8 mb from Newport to Salem and +1.0 mb from Salem to Redmond.

Upper level trough will remain in place today. Afternoon heating will likely provide some cloud buildups and potential scattered showers. Moisture amounts are expected to be very light. Wind flow will be mostly light and variable through the morning then increase from NW to N early this afternoon to 5 - 10 mph.

TODAY'S FORECAST:

Mostly cloudy with a chance of showers.

Salem's high temperature today will be near 80 degrees (average is 82).

Relative humidity: Will drop below 60 percent around 10:00 a.m. and reach a low of about 38 percent around 4 p.m.

Surface winds: Light and variable this morning, becoming NW to N at 5 - 10 mph during the afternoon.

Transport winds: Light and variable this morning below 3000 ft and S to SW at 5 - 10 mph above 3000 ft. Transport wind shifting to NW to N at 5 - 10 mph this afternoon.

Mixing height: Near or above 5000 ft throughout the day.

Salem's sunset tonight: 8:57 p.m.

(Salem Airport data for Sunday, Jul 12: High 83°F; Rainfall: .00")

(Maximum Ventilation Index expected today: 50)

EXTENDED DISCUSSION:

Upper level trough remains over the state through the week but weakens. This will allow more clearing each day. Temperatures will generally remain seasonably warm. Wind will be light during the overnight to early morning hours, favoring a northerly flow. Afternoon winds increase but remain mostly northerly. Expect poorer mixing during the night and morning hours but continued good mixing during the 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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