[willamette-fcst] Field Burning Forecast - September 19, 2017
Willamette Valley Field Burning Forecast
willamette-fcst at listsmart.osl.state.or.us
Tue Sep 19 08:40:25 PDT 2017
SILVERTON HILLS FIELD BURNING FORECAST
OREGON DEPARTMENT OF FORESTRY WEATHER OFFICE
8:45 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. Approximately 0.91 inches fell in the last 24 hours in Salem, mostly before sunrise today. The Silverton Hills could see another 1.25-1.50 inches of rain fall before sunrise Wednesday. Small hail is possible with larger thunderstorms this afternoon.
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 between Monday night and the arrival of the Autumnal Equinox on Friday morning, 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. 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
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