[willamette-fcst] Field Burning Forecast - September 19, 2017 (Noon Update)

Tue Sep 19 11:43:16 PDT 2017

SILVERTON HILLS FIELD BURNING FORECAST
OREGON DEPARTMENT OF FORESTRY WEATHER OFFICE
11:45 AM PDT TUE SEP 19, 2017

BURN ADVISORY:

Agricultural burning is recommended to be limited to the hours of 8 a.m. to 5 p.m.

Prep burning is not allowed.

WEATHER DISCUSSION:

A strong upper-level disturbance remains over the Pacific Northwest, with scattered showers and isolated thundershowers in the Cascades. A brief pause in showers will end soon, as more storms move into the Willamette Valley. The Silverton Hills could see another inch or more of rain fall before sunrise Wednesday. Small hail is possible with larger thunderstorms later this evening.

TODAY'S FORECAST:

Windy with Thundershowers. Small Hail possible.

Salem's high temperature today will be near 61°F (average is 76°F).
Relative humidity:  60% or higher for the next 24 hours.
Surface winds: S-SW 10-15 mph this morning, becoming SW 15-25 mph this afternoon.
Transport winds: W 30 mph this morning, becoming W-SW 25-35 mph this afternoon.
Mixing height: Above 5000 feet for the next 24 hours.
Salem's sunset tonight: 7:14 p.m.

(Salem Airport data for Sunday, September 18th: High 63°F; Rainfall: .91")
(Maximum Ventilation Index expected today: 175)

EXTENDED DISCUSSION:

Fall weather continues with little to no change before the arrival of the Autumnal Equinox on Thursday night, when the calendar "officially" marks the end of the 2017 summer. The jet stream will remain over southern Oregon, bringing polar air and stormy weather for the next several days, keeping temperatures well below seasonal averages. An upper-level ridge will slowly form over the Pacific, but cloud cover will continue to spill over it through the early weekend; this will limit drying until the ridge moves overhead early next week.

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

Tom Jenkins, AEM
ODF Meteorologist
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://omls.oregon.gov/pipermail/willamette-fcst/attachments/20170919/a54b4940/attachment.html>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: fbs.htm.doc
Type: application/msword
Size: 29696 bytes
Desc: fbs.htm.doc
URL: <https://omls.oregon.gov/pipermail/willamette-fcst/attachments/20170919/a54b4940/attachment.doc>