[willamette-fcst] Silverton Hills AM Forecast_Gary.doc

Tue Jul 19 08:58:22 PDT 2016

SILVERTON HILLS FIELD BURNING FORECAST

OREGON DEPARTMENT OF FORESTRY WEATHER OFFICE

8:55 AM PDT TUE JUL 19, 2016

BURN ADVISORY:

Agricultural burning is not recommended.

Prep burning is not allowed.

WEATHER DISCUSSION:

An upper-level trough, centered just off the northern Oregon coast continues to cause cool, moist, and somewhat unstable and SW flow aloft over Oregon. A deep marine layer will keep skies mostly cloudy this afternoon but also allow for excellent mixing with light SW transport winds turning W by late afternoon. Gradient stacking is currently balanced and may be favorable this afternoon as skies east of the Cascades clear.

Salem's high temperature today will be near 77°F (average is 83°F).

Relative humidity:  Dropping below 60% about 10:00 a.m. and around 45% by 2:00 p.m.

Surface winds: SSW 3 mph increasing 6-9 mph during the afternoon then W 6-8 mph by 5:00 p.m.

Transport winds: SW 8-10 mph shifting to W by 5:00 p.m.

Mixing height: Rising to 3500 feet by 11:00 a.m. and then 5000 feet by 2:00 p.m.

Salem's sunset tonight: 8:52 p.m.

(Salem Airport data for Monday, July 18th: High 76°F; Rainfall: .00")

(Maximum Ventilation Index expected today: 50)

EXTENDED DISCUSSION:

Conditions on Wednesday will be similar though with a little higher chance of showers. The upper level trough is expected to move across Oregon and Washington on Thursday night and Friday. Mostly cloudy skies, onshore flow and good mixing heights will persist through Friday with somewhat more sun in the afternoons. Then sunnier and warmer for the weekend.

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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