[willamette-fcst] Silverton Hills AM Forecast_Pete.doc

Fri Sep 1 08:56:50 PDT 2017

SILVERTON HILLS FIELD BURNING FORECAST

OREGON DEPARTMENT OF FORESTRY WEATHER OFFICE

8:55 AM PDT FRI SEP 1, 2017

BURN ADVISORY:

Agricultural burning is not recommended.

Prep burning is not allowed.

WEATHER DISCUSSION:

A building upper-level ridge will greatly suppress mixing today, as a surface thermal trough builds northward along the coast.  Hot surface temperatures, low humidity, and increasing offshore flow will likely combine to put the valley into State Fire Marshal Burn-Ban Conditions later this afternoon.

TODAY'S FORECAST:

Sunny, hot, and breezy.

Salem's high temperature today will be near 96°F (average is 80°F).

Relative humidity:  Dropping to 45% by 11 a.m. and to 30% by 2 p.m.

Surface winds: N 5-10 mph this morning; N 10-15 mph this afternoon.

Transport winds: NE 10-15 mph this morning; NE 15-20 mph this afternoon.

Mixing height: Only rising to 2500 feet by 5 p.m.

Salem's sunset tonight: 7:48 p.m.

(Salem Airport data for Thursday, August 31st: High 86°F; Rainfall: .00")

(Maximum Ventilation Index expected today: 50)

EXTENDED DISCUSSION:

Temperatures will climb to around 100°F Saturday through Tuesday.  In addition, a developing southerly flow aloft will likely force wildfire smoke back over the region by Sunday.

Increasing southerly flow aloft may transport enough moisture and instability northward for thunderstorm development by the middle of next week, as temperatures slowly begin to moderate.  It is too soon to tell if the cooling trend will create burning opportunities.

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.

     5. In accordance with OAR 837-110-0090, all field burning shall be
         banned when any two of the following criteria are present:
         A. Temperature of 95 degrees Fahrenheit or above
         B. Relative humidity of 30 percent or below
         C. Wind speed of 15 miles per hour or higher

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

Pete Parsons

ODF Meteorologist

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://omls.oregon.gov/pipermail/willamette-fcst/attachments/20170901/581e6c8d/attachment.html>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: Silverton Hills AM Forecast_Pete.doc
Type: application/msword
Size: 36864 bytes
Desc: Silverton Hills AM Forecast_Pete.doc
URL: <https://omls.oregon.gov/pipermail/willamette-fcst/attachments/20170901/581e6c8d/attachment.doc>