[willamette-fcst] Silverton Hills AM Forecast.doc

[Willamette Valley Field Burning Forecast]

SILVERTON HILLS FIELD BURNING FORECAST

OREGON DEPARTMENT OF FORESTRY WEATHER OFFICE

9:00 AM PDT TUE JUL 9, 2013



BURN ADVISORY:



Recommended burn times for agricultural burning from noon until 7:00 p.m.

Prep burning is not allowed.



WEATHER DISCUSSION:



An upper-level ridge remains centered over the southwestern US with a warm and dry southwesterly flow aloft over Oregon. The air aloft over western Oregon has warmed several degrees over the past 24 hours, and onshore flow has decreased.



Satellite imagery shows marine clouds confined mostly to west of the coast range, so a full day of sunshine will help valley temperatures climb to near 90 degrees this afternoon.  Transport winds should remain mostly northerly.



TODAY'S FORECAST:



Sunny and warmer.



Salem's high temperature today will be near 90 degrees (normal is 81).

Relative humidity:  Drops below 60% by 11 a.m. and to near 30% by 5 p.m.

Surface winds:  N 3-8 mph this morning; NNW 7-15 mph later this afternoon.

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

Mixing height: Rising to near 4000 feet this afternoon.

Salem's sunset tonight: 8:59 p.m.



(Salem Airport data for Monday, July 8th: High 85°F; Rainfall .00")

(Maximum Ventilation index expected today: 60)



EXTENDED DISCUSSION:



An approaching upper-level trough will increase the southwesterly flow aloft on Wednesday.  Increasing onshore flow may bring some morning marine clouds into the Willamette Valley.  Otherwise, expect sunshine but with cooler temperatures.  Transport winds are forecast to turn northwesterly in the afternoon with cooling aloft improving mixing.



A weak upper-level trough will move over Oregon Thursday and Friday.  No showers are expected, but strong onshore flow should blanket the Willamette Valley with morning low clouds.  Temperatures will cool back into the mid 70s with partly cloudy skies in the afternoons.



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 15mph.



     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 and the Oregon Department of Forestry.  For information contact ODA at 503-986-4701.



Pete Parsons

ODF Meteorologist
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://omls.oregon.gov/pipermail/willamette-fcst/attachments/20130709/ba299882/attachment.html>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: Silverton Hills AM Forecast.doc
Type: application/msword
Size: 31232 bytes
Desc: Silverton Hills AM Forecast.doc
URL: <https://omls.oregon.gov/pipermail/willamette-fcst/attachments/20130709/ba299882/attachment.doc>