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SILVERTON HILLS FIELD BURNING FORECAST
OREGON DEPARTMENT OF FORESTRY WEATHER OFFICE
12:00 PM PDT MON SEP 26 2011
BURN ADVISORY:
Recommended burn times for agricultural burning are from now until 5:00pm.
Prep burning is not allowed.
Propane flaming is not allowed.
WEATHER DISCUSSION:
A warm front which brought rain to the Willamette Valley overnight and early this morning
has shifted northward leaving mainly just clouds over the region as of late morning. An
associated cold front is lurking off the coast and should bring rain back to the valley
again tonight. Amounts of a third to a half an inch are likely by tomorrow morning.
Wet fields, unfavorable southerly winds, strong wind speeds and high humidities will
preclude open field burning this afternoon.
THIS AFTERNOON'S FORECAST:
Salem's high temperature today will be near 71.
Minimum relative humidity 55%.
Surface winds: Southerly 10-15g20 mph this afternoon decreasing to 5-10 mph this evening.
Transport winds: SSW 25-35 mph
Maximum mixing height: 6800 feet.
Sunset tonight: 7:02 pm
THREE-HOURLY DATA:
2pm 5pm 8pm
Temperature: 68 69 64
Relative Humidity: 55% 61% 81%
Surface Wind Direction: 180 190 180
Surface Wind Speed: 19 17 7
Transport Wind Direction: 214 230 230
Transport Wind Speed: 32 27 21
Estimated Mixing Height: 6800 4300 2800
Ventilation Index: 218 116 59
EXTENDED DISCUSSION:
Expect rain tonight and early tomorrow.
An upper level ridge should bring drier weather late Tomorrow through early Friday. Best
chance for another burn opportunity would be Thursday or possibly Friday if the next
batch of rain holds off long enough.
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:260911:1153
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