[willamette-fcst] Silverton Hills AM Forecast_Pete.doc

[Willamette Valley Field Burning Forecast]

SILVERTON HILLS FIELD BURNING FORECAST

OREGON DEPARTMENT OF FORESTRY WEATHER OFFICE

8:55 AM PDT FRI JUL 28, 2017



BURN ADVISORY:



Agricultural burning is not recommended.



Prep burning is allowed from noon until 2 p.m. with a 50 acre limit.



WEATHER DISCUSSION:



A dry and stable WSW flow aloft is continuing over Oregon.  This morning's sounding over Salem showed an almost identical temperature profile to yesterday morning.  The difference is that onshore flow is much weaker today.



With an absence of marine low clouds, sunny skies will warm surface temperatures to seasonal averages this afternoon, possibly balancing this morning's negative gradient stacking.  However, transport winds may stay too northerly to allow for burning.



TODAY'S FORECAST:



Patchy morning clouds, then sunny and seasonably warm.



Salem's high temperature today will be near 85°F (average is 84°F).

Relative humidity:  Dropping to 60% by 11 a.m. and to near 35% by 5 p.m.

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

Transport winds: NNE 10 mph this morning; NNW 10-15 mph this afternoon.

Mixing height: Rising to 3000 feet around noon and to 4500 feet by 5 p.m.

Salem's sunset tonight: 8:43 p.m.



(Salem Airport data for Thursday, July 27th: High 81°F; Rainfall: .00")

(Maximum Ventilation Index expected today: 70)



EXTENDED DISCUSSION:



A building upper-level ridge will bring sunny and warmer weather this weekend through at least the first half of next week.  Temperatures will warm to near 90°F over the weekend and could peak near 100°F by next Wednesday. Increasing onshore flow is expected to initiate a cooling trend late next week.  It is too soon to tell if that will create any 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.



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/20170728/c346f007/attachment.html>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: Silverton Hills AM Forecast_Pete.doc
Type: application/msword
Size: 36352 bytes
Desc: Silverton Hills AM Forecast_Pete.doc
URL: <https://omls.oregon.gov/pipermail/willamette-fcst/attachments/20170728/c346f007/attachment.doc>