[willamette-fcst] Silverton Hills AM Forecast_Gary.doc

Fri Sep 23 11:36:37 PDT 2016

SILVERTON HILLS FIELD BURNING FORECAST

OREGON DEPARTMENT OF FORESTRY WEATHER OFFICE

11:35 AM PDT FRI SEPT 23, 2016

BURN ADVISORY:

Agricultural burning is not recommended.

Prep burning is not allowed.

WEATHER DISCUSSION:

A storm system has arrived over northwest Oregon this morning even though it is gradually weakening. Strong south winds will increase this morning with possible gusts to 30 mph then decrease late in the afternoon and evening. The showers have decreased though periods of light showers will occur through the afternoon. Additional rainfall will be a tenth of an inch or less. The clouds and showers will keep conditions moist with low mixing heights most of the day, and negative pressure gradients. No burning opportunity is expected today.

TODAY's FORECAST

Cloudy and windy with showers.

Salem's high temperature today will be near 61°F (average is 75°F).

Relative humidity: Dropping to around 75% in mid-afternoon.

Surface winds: S 14-20 mph with gusts possible to 30 mph.

Transport winds: S 18-23 mph.

Mixing height: Currently around 500 feet, rising to about 3500 feet by late afternoon.

Salem's sunset tonight: 7:06 p.m.

(Salem Airport data for Thursday, September 22nd: High 71°F; Rainfall: Trace)

(Maximum Ventilation Index expected today: 80)

EXTENDED DISCUSSION:

No rain is expected this weekend and drying conditions will be good, especially on Sunday as a strong ridge builds over the valley. Models are unsettled about transport winds early next week and they no longer show Monday with favorable winds. Each day of the week shows some potential for burning but it appears too early to determine which day might be best.

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/20160923/626490fe/attachment.html>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: Silverton Hills AM Forecast_Gary.doc
Type: application/msword
Size: 31232 bytes
Desc: Silverton Hills AM Forecast_Gary.doc
URL: <https://omls.oregon.gov/pipermail/willamette-fcst/attachments/20160923/626490fe/attachment.doc>