[willamette-fcst] Silverton Hills Midday Forecast_Pete.doc

[Willamette Valley Field Burning Forecast]

SILVERTON HILLS FIELD BURNING FORECAST

OREGON DEPARTMENT OF FORESTRY WEATHER OFFICE

11:55 AM PDT MON SEP 19, 2016



BURN ADVISORY:



Agricultural burning is not recommended.



Prep burning is not allowed.



WEATHER DISCUSSION:



An autumn-like weather system dumped about three-quarters of an inch of rain across the region this past weekend.  As a result, fields are still too damp for burning today.



Strong WSW flow aloft is sending numerous showers across Washington and a few showers into extreme northern Oregon.  Mostly cloudy skies extend southward across Marion County and much of Linn County.  Light showers can't be ruled out this afternoon.  Temperatures will remain below average.



TODAY'S FORECAST:



Mostly cloudy.  Chance of light showers.



Salem's high temperature today will be near 69°F (average is 76°F).

Relative humidity:  Dropping to 60% around 1 p.m. and to near 45% by 5 p.m.

Surface winds: SW 5 mph; becoming W 5 mph this afternoon...turning NW late.

Transport winds: SW 5-10 mph; becoming W 10 mph this afternoon...NW late.

Mixing height: Rising to 3000 feet around 1 p.m. and to 5000 feet by 5 p.m.

Salem's sunset tonight: 7:14 p.m.



(Salem Airport data for Sunday, September 18th: High 73°F; Rainfall: Trace")

(Maximum Ventilation Index expected today: 50)



EXTENDED DISCUSSION:



SW flow aloft and light NW transport winds may provide favorable burning conditions on Tuesday, if fields are dry enough.  Gradient-stacking may also be a limiting factor. An upper-level trough is projected to move over the region on Wednesday, which will increase the chance of showers but may also  produce favorable burning conditions, if fields are dry enough.  High pressure will bring drying and warming late in the 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.



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/20160919/20a551e6/attachment.html>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: Silverton Hills Midday Forecast_Pete.doc
Type: application/msword
Size: 35840 bytes
Desc: Silverton Hills Midday Forecast_Pete.doc
URL: <https://omls.oregon.gov/pipermail/willamette-fcst/attachments/20160919/20a551e6/attachment.doc>