[willamette-fcst] Willamette Valley Field Burning Forecast

Tue Jul 15 08:47:44 PDT 2014

SILVERTON HILLS FIELD BURNING FORECAST

OREGON DEPARTMENT OF FORESTRY WEATHER OFFICE

8:45 AM PDT TUE JUL 15, 2014

BURN ADVISORY:

Agricultural burning is not recommended.

Prep burning is not allowed.

WEATHER DISCUSSION:

Upper level ridge will dominate the weather today. Marine low clouds seeped into the coastal corridors and into the Portland metro area this morning, otherwise skies are clear. Current pressure gradients are +2.4 mb from Newport to Salem and -0.3 mb from Salem to Redmond.

With a broad upper level ridge over the area today, temperatures should soar into the mid to upper 90s. Fire Marshal conditions for high temperatures and low humidities are very possible between 4 - 6 p.m. Expect northerly flow through the Willamette Valley. Mixing heights will remain fairly low most of the day with maximum mixing getting no higher than 4000 ft despite strong heating.

TODAY'S FORECAST:

Clear, sunny and hot.

Salem's high temperature today will be near 96 degrees (average is 82).

Relative humidity: Dropping to 60% by 11 a.m. and dropping to 25 - 30 percent around 4 p.m.

Surface winds: Northerly at 3 - 7 mph this morning increasing to northerly at 5 - 10 mph this afternoon.

Transport winds: N to NNE at 5 - 10 mph during the morning increasing to N to NNE at 8 - 13 mph this afternoon.

Mixing height: Morning below 2500 ft, rising to near 3000 ft by 2 p.m. and to 3500 - 4000 ft by 5 p.m.

Salem's sunset tonight: 8:55 p.m.

(Salem Airport data for Wednesday, July 14th: High 92°F; Rainfall: .00")

(Maximum Ventilation Index expected today: 40)

EXTENDED DISCUSSION:

Ridge begins flattening Wednesday opening the door to NW winds and potential burn opportunities. High temperatures moderate from the 90s to near 80 by Friday and into the weekend. Maximum mixing heights improve to 4000 - 5000 ft.

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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