[willamette-fcst] Silverton Hills Midday Forecast_Gary.doc

[Willamette Valley Field Burning Forecast]

SILVERTON HILLS FIELD BURNING FORECAST

OREGON DEPARTMENT OF FORESTRY WEATHER OFFICE

11:50 AM PDT FRI JUL 8, 2016


BURN ADVISORY:



Recommended times for agricultural burning are from now until 700 p.m.



Prep burning is not allowed.



WEATHER DISCUSSION:



Widespread clouds remain over the valley at this hour though the only showers are developing on the Cascade slopes. The potential for showers will increase in the afternoon and a thundershower is not out of the question by late afternoon and through the evening. These would be in response to an unseasonably strong upper low moving southeast towards the coast and an upper level jet moving over the area. Rainfall may exceed a quarter-inch, especially in the heavier showers.



TODAY'S FORECAST:



Mostly cloudy with showers increasing by late afternoon, and a thundershower possible late.



Salem's high temperature today will be near 74°F (average is 81°F).

Relative humidity:  Dropping below 60% near 2 p.m.

Surface winds: SSW 6-10 mph becoming SSW 10-15 mph later in the afternoon.

Transport winds: SSW 12-15 mph increasing to 17-21 mph later in the afternoon.

Mixing height: At or above 5000 feet.

Salem's sunset tonight: 8:59 p.m.



(Salem Airport data for Thursday, July 8th: High 72°F; Rainfall: .05")

(Maximum Ventilation Index expected today: 100)



EXTENDED DISCUSSION:



Cool weather with showers will continue Saturday and Sunday as the upper low passes over the state. Drier weather is expected on Monday and Tuesday but onshore flow will continue. This will cause clouds and continued unseasonably cool weather, and possibly light showers as a weak cold front approaches Monday night or Tuesday.



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



Gary Votaw

ODF Meteorologist

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