[willamette-fcst] Willamette Valley Field Burning Forecast - Noon Update

[Willamette Valley Field Burning Forecast]

SILVERTON HILLS FIELD BURNING FORECAST

OREGON DEPARTMENT OF FORESTRY WEATHER OFFICE

11:45 AM PDT MON JUL 21, 2014



BURN ADVISORY:



Agricultural burning is not recommended.

Prep burning is not allowed.



WEATHER DISCUSSION:



Upper level low is northwest of Vancouver Island this morning. It is currently swinging another frontal band into the state, mainly to the south. Radar is showing scattered light moisture to the south of Eugene. Clouds continue to stream in from the southwest. Current pressure gradients are +1.7 mb from Newport to Salem and +2.0 mb from Salem to Redmond.



Upper low will slowly move toward the state today keeping skies mostly cloudy. Moisture appears to be dissipating as it moves into northern Lane County so not really expecting any afternoon moisture in the northern Willamette Valley. Gradient stacking is starting to shift and should continue. This will likely give some burn opportunities this afternoon. Cloud cover will keep mixing levels fairly low until the afternoon hours.



TODAY'S FORECAST:



Mostly Cloudy.



Salem's high temperature today will be near 78 degrees (average is 83).

Relative humidity: Dropping to near 40 percent around 4 p.m.

Surface winds: Northerly at 5 - 10 mph becoming NW to NNW 5 - 10 mph later this afternoon.

Transport winds: Northerly early, becoming to WNW to NNW at 5 - 10 mph later this afternoon.

Mixing height: Rising to near 3000 ft by 1 p.m. and to 4500 - 5000 ft by 5 p.m.

Salem's sunset tonight: 8:50 p.m.



(Salem Airport data for Wednesday, July 14th: High 75°F; Rainfall: .00")

(Maximum Ventilation Index expected today: 50)



EXTENDED DISCUSSION:



Upper level low moves closer to the state tomorrow with shower activity potentially increasing during the afternoon hours. Wind flow looks like it will turn westerly sooner than today opening up a burn opportunity if moisture doesn't arrive too soon. Low eventually moves into the state Wednesday bringing more showers and probably wetting fields. Flat ridge will follow on Thursday and Friday bringing drying and warming. Wind flow will likely turn northerly.



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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