[willamette-fcst] Willamette Valley Field Burning Forecast

Mon Jul 7 08:46:30 PDT 2014

SILVERTON HILLS FIELD BURNING FORECAST

OREGON DEPARTMENT OF FORESTRY WEATHER OFFICE

8:45 AM PDT MON JUL 7, 2014

BURN ADVISORY:

Agricultural burning is not recommended.

Prep burning is not allowed.

WEATHER DISCUSSION:

Broad upper level trough built over the state through the weekend and will remain over the state today. A minor influx of marine air moved into the Willamette Valley last night with the satellite pictures showing clouds banked along the coast and pushing into the Coast Range corridors this morning. Current gradients are a +2.2 mb from Newport to Salem and -0.1 mb from Salem to Redmond. The morning sounding shows a deep stable layer with mixing height below 1000 ft and NNW to NNE winds at 5-10 mph.

Upper ridge will remain over the state today. Marine low clouds to our west will quickly dissipate.  Expect another sunny and hot day with the temperatures reaching 90+ in the Willamette Valley. Wind flow will be light northerly. Mixing will remain mostly poor during the morning but daytime heating should lift mixing heights to 4000 - 5000 ft during the late afternoon.

TODAY'S FORECAST:

Clear and very warm.

Salem's high temperature today will be near 92 degrees (average is 80).

Relative humidity: Dropping to 60% around 9 a.m. and to 28% by 4 p.m.

Surface winds: NNW to N 3-6 mph this morning; NNW to N 7-12 mph this afternoon.

Transport winds: Mostly northerly at 6 - 12 mph throughout the day.

Mixing height: Morning below 2500 ft, rising to near 3000 by 1 p.m. and to 4500 ft by 5 p.m.

Salem's sunset tonight: 9:00 p.m.

(Salem Airport data for Wednesday, July 6th: High 91°F; Rainfall: .00")

(Maximum Ventilation Index expected today: 54)

EXTENDED DISCUSSION:

Upper ridge shifts to the east tomorrow with a minor marine push moving in tomorrow late afternoon and evening. Some thunderstorms are likely over the Cascades Tuesday evening. Wind flow will become more northwesterly during the day but remain mostly northerly during the night and early morning hours. Daytime high temperatures will lower several degrees over the next few days. Ridge starts to rebuild late in the week.

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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