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SILVERTON HILLS FIELD BURNING FORECAST
OREGON DEPARTMENT OF FORESTRY WEATHER OFFICE
9:00 AM PDT MON SEP 26 2011
BURN ADVISORY:
Recommended burn times for agricultural burning are from 11:00am to 5:00pm.
Prep burning is not allowed.
Propane flaming is not allowed.
WEATHER DISCUSSION:
Surface weather maps show a strong fall Pacific weather system moving into the Pacific
Northwest today. The system is quite wet, with moisture originating in the tropics.
Initially a warm front will move through the area this morning followed by a cold front
tonight. It will be quite windy and high wind warnings are out for the Oregon coast
north of Lincoln City. Winds in the Valley could reach 25mph. By tomorrow morning
rainfall amounts of a third to a half an inch are likely in the central Willamette
Valley.
Wet fields, strong winds with an unfavorable southerly direction will preclude burning
today.
TODAY'S FORECAST:
Cloudy, rainy and mild.
Salem's high temperature today will be near 71.
Minimum relative humidity 55%.
Surface winds: S 10-15g25.
Transport winds: S to SW 25-35 decreasing to 8-15 this evening.
Maximum mixing height: 6800 feet.
Sunset tonight: 7:01 pm.
THREE-HOURLY DATA:
11am 2pm 5pm 8pm
Temperature: 64 70 70 63
Relative Humidity: 65% 55% 61% 78%
Surface Wind Direction: 160 180 190 210
Surface Wind Speed: 17 17 13 7
Transport Wind Direction: 200 214 230 230
Transport Wind Speed: 29 32 27 21
Estimated Mixing Height: 5500 6800 4300 2800
Ventilation Index: 160 218 116 59
EXTENDED DISCUSSION:
Rain continues 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:260911:0813
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