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SILVERTON HILLS FIELD BURNING FORECAST
OREGON DEPARTMENT OF FORESTRY WEATHER OFFICE
12:00 PM PDT TUE AUG 14 2012
BURN ADVISORY:
Agricultural burning burning is not recommended.
Prep burning is allowed from 2:00pm to 5:00pm with a 50 acre limit.
Propane flaming is allowed from 2:00pm to 5:00pm.
WEATHER DISCUSSION:
Sunny and warm weather continues over the Willamette Valley. Satellite pictures show
Oregon nearly cloud free. Temperatures are running about 1 to 2 degrees cooler than
yesterday at the same time.
Latest computer models show a generally northerly wind today in the transport region.
Pressure gradients as of 11am included: Newport to Salem, 1.0 mb onshore; Salem to
Redmond, 1.3 mb onshore for a total Newport to Redmond gradient of 2.3 mb onshore. The
Portland to Medford pressure difference was 2.8 mb northerly.
A mid-afternoon pibal will test the transport wind forecast but the likelyhood of open
field burning today is nil.
THIS AFTERNOON'S FORECAST:
Salem's high temperature today will be near 91.
Relative humidity drops to 50% by 10am. Minimum relative humidity 29%.
Surface winds:
Transport winds:
Maximum mixing height:
Sunset tonight: 8:19 pm
THREE-HOURLY DATA:
2pm 5pm 8pm
Temperature: 87 91 81
Relative Humidity: 31% 29% 44%
Surface Wind Direction: 010 010 330
Surface Wind Speed: 5 6 7
Transport Wind Direction: 300 300 320
Transport Wind Speed: 16 16 15
Estimated Mixing Height: 5000 5500 1500
Ventilation Index: 80 88 22
EXTENDED DISCUSSION:
Look for strong upper level ridging over the Pacific Northwest through the end of the
week. This will bring very warm temperatures to the area. Highs will be near or slightly
above 100 degrees at least through Friday. Low level flow will be offshore or easterly
for no burning opportunities. In addition Fire Marshal conditions will likely go into
effect during the afternoon hours through Friday. Upper level flow will turn more
southerly by late Friday. Possibly Friday and more likely Saturday, thunderstorms are
likely at least over the mountains.
The National Weather Service’s digital forecast is available at:
<a
href="http://forecast.weather.gov/MapClick.php?lat=44.905&lon=-122.810">http://forecast.weather.gov/MapClick.php?lat=44.905&lon=-122.810</a>.
Notes:
1. Mixing height, as used here, is the lowest height at which the
potential temperature exceeds the equivalent 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 times
the transport wind speed 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.
Jim Little
ODF Meteorologist
jlwx:140812:1139
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