[willamette-fcst] fbs.docx

Thu Jul 21 11:48:10 PDT 2016

SILVERTON HILLS FIELD BURNING FORECAST

OREGON DEPARTMENT OF FORESTRY WEATHER OFFICE

11:45 AM PDT THU JUL 21, 2016

BURN ADVISORY:

Agricultural burning is not recommended.

Prep burning is not allowed.

WEATHER DISCUSSION:

An unseasonably strong upper-level trough is approaching the Oregon coast. Warm air aloft continues to slow down the rise of the mixing height and a marine push is still expected to arrive in mid-afternoon. Pressure gradient stacking should be positive and showers will hold off until evening. The best burn potential appears to be early afternoon.

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

Relative humidity:  Dropping to near 40% by 2:00 p.m.

Surface winds: N 4-7 mph becoming W 9-14 mph by 4:00 p.m.

Transport winds: NW 5-8 mph shifting to W 12-16 mph by 3:00 p.m. and continuing into evening.

Mixing height: Rising to 3000 feet by 1:00 p.m. and 4000 feet by 3:00 p.m.

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

(Salem Airport data for Wednesday, July 20th: High 85°F; Rainfall: .00")

(Maximum Ventilation Index expected today: 60)

EXTENDED DISCUSSION:

About a tenth of an inch of rainfall can be expected tonight for much of the area. Marine air will dominate the valley on Friday with essentially no burning potential. Onshore flow will weaken through the weekend and no further showers are expected.

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

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://omls.oregon.gov/pipermail/willamette-fcst/attachments/20160721/d22655cc/attachment.html>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: fbs.htm.doc
Type: application/msword
Size: 35840 bytes
Desc: fbs.htm.doc
URL: <https://omls.oregon.gov/pipermail/willamette-fcst/attachments/20160721/d22655cc/attachment.doc>