[willamette-fcst] Field Burning Forecast - August 16, 2017
Willamette Valley Field Burning Forecast
willamette-fcst at listsmart.osl.state.or.us
Wed Aug 16 08:55:58 PDT 2017
SILVERTON HILLS FIELD BURNING FORECAST
OREGON DEPARTMENT OF FORESTRY WEATHER OFFICE
8:50 AM PDT WED AUG 16, 2017
BURN ADVISORY:
Agricultural burning is not recommended.
Prep burning is allowed between 12 p.m. and 2 p.m. with a 50 acre limit.
WEATHER DISCUSSION:
A weak upper-level ridge approaches Oregon today, turning flow NW aloft as it arrives. Surface onshore gradients will steadily build and should be positively stacked by mid-afternoon. Surface wind direction will remain the limiting factor, as transport winds will turn NW early this afternoon. A deep marine push will enter the valley by sunset, and bring extensive cloud cover overnight.
TODAY'S FORECAST:
Mostly Clear with Increasing Clouds late this afternoon.
Salem's high temperature today will be near 86°F (average is 83°F).
Relative humidity: Below 60% by 9 a.m. and nearing 35% by 5 p.m.
Surface winds: N 5-10 mph this morning, becoming NW 5-10 mph after 3 p.m.
Transport winds: N 5-10 mph this morning, becoming NW 5-10 mph after 1 p.m.
Mixing height: Rising to 3000 feet by 12 p.m. and reaching 5000 feet by 3 p.m.
Salem's sunset tonight: 8:16 p.m.
(Salem Airport data for Tuesday, August 15th: High 83°F; Rainfall: .00")
(Maximum Ventilation Index expected today: 50)
EXTENDED DISCUSSION:
The upper-level ridge will loiter over western Oregon on Thursday, turning flow aloft light as mixing is suppressed. Clouds in the valley will be slow to break up, keeping temperatures mild for the entire day. The upper-level ridge will begin to weaken and flatten out as Thursday night progresses, allowing W flow aloft to begin cooling the atmosphere again. Onshore surface gradients may develop early on Friday morning, and mixing heights will no longer be limited as sunshine falls upon the Willamette Valley, indicating potential field burning opportunities ahead of the weekend.
Weather appears mild for the Eclipse Weekend, as a weak upper-level disturbance pushes across the Willamette Valley and stalls out along the California coast early next week. This passing feature will generate some clouds to provide cooling shade to the Silverton Hills, but no rainfall is expected. Fair weather should persist through Monday for the Oregon Eclipse, but models indicate a potential turn to offshore flow with temperatures returning above seasonal averages next week after the Sun reappears; this scenario will be evaluated further as it could pull regional wildfire smoke across the Cascades 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/20170816/260424cf/attachment.html>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: fbs.htm.doc
Type: application/msword
Size: 30720 bytes
Desc: fbs.htm.doc
URL: <https://omls.oregon.gov/pipermail/willamette-fcst/attachments/20170816/260424cf/attachment.doc>
More information about the willamette-fcst
mailing list