[willamette-fcst] Silverton Hills Field Burning Forecast - Morning update

[Willamette Valley Field Burning Forecast]

SILVERTON HILLS FIELD BURNING FORECAST

OREGON DEPARTMENT OF FORESTRY WEATHER OFFICE

8:45 AM PDT MON JUL 6, 2015



BURN ADVISORY:



Recommended times for agricultural burning are from noon until 7 p.m.



Prep burning is not allowed.



WEATHER DISCUSSION:



Upper level split flow pattern remains over the Pacific Northwest with an upper level ridge to the north and a weak upper low to the south. Skies are mostly clear in the Willamette Valley this morning with marine low clouds pushing into the coastal gaps this morning. Morning sounding shows a stable layer up through 5000 ft. Low level wind flow is W to NW at 3 - 6 mph up to about 2000 ft, turning SW'erly at 8 - 15 mph above. Pressure gradients are +2.5 mb from Newport to Salem and +.4 mb from Salem to Redmond.



Expect little change in the split upper level flow today. Some cloud buildups will form over the Cascades this afternoon. Wind flow will not change much as well with mostly a light SW to NW flow.



TODAY'S FORECAST:



Mostly sunny.



Salem's high temperature today will be near 93 degrees (average is 80).

Relative humidity: Will drop below 60 percent by 9:00 a.m. and reach a low of about 26 percent around 4 p.m.

Surface winds: SW to W at 3 - 7 mph this morning then shifting to WSW to WNW at 5 - 10 mph during the afternoon.

Transport winds: SW to NW at 5 - 10 mph through the day.

Mixing height: Below 3000 ft until near noon, rising to 4000 ft by 2 p.m. and near 5000 ft around 4 p.m.

Salem's sunset tonight: 9:01 p.m.



(Salem Airport data for Sunday, Jul 5: High 96°F; Rainfall: .00")

(Maximum Ventilation Index expected today: 35)



EXTENDED DISCUSSION:



Upper level flow remains split with the pattern slowly moving inland through the week. Upper low expands northward bringing a greater possibility of late afternoon to evening thunderstorms beginning Wednesday. Wind flow will be mostly light and variable overnight with NW flow at 5 - 10 mph through the day. Wind flow turns more SW to W later in the week. Afternoon temperatures gradually cool.

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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