<pre>
<!DOCTYPE HTML PUBLIC -//W3C//DTD HTML 4.0 Transitional//EN>
<html>
<head>
</head>
<body>
<pre>
SILVERTON HILLS FIELD BURNING FORECAST
OREGON DEPARTMENT OF FORESTRY WEATHER OFFICE
12:00 PM PDT TUE SEP 04 2012
BURN ADVISORY:
Agricultural burning burning is not recommended.
Prep burning is not allowed.
Propane flaming is allowed from now until 5:00pm.
WEATHER DISCUSSION:
Sunny skies prevail over all of Oregon except for the immediate coastal areas as of late
morning. Temperatures are running about 2 to 6 degrees warmer than yesterday at the same
time through the Willamette Valley.
Low level winds are mostly northerly or slightly northeasterly. The ODF SODAR system in
the central coast range shows from the northeast around 15-25 mph between about 700 and
2600 feet above ground level.
Models indicate the unfavorable northerly winds continuing with no shift this afternoon.
THIS AFTERNOON'S FORECAST:
Sunny and warm.
Salem's high temperature today will be near 85.
Relative humidity drops to 50% by 12pm. Minimum relative humidity 29%.
Surface winds: Northerly 7-10 mph.
Transport winds: Northerly 15-20 mph.
Maximum mixing height: 4500 feet.
Sunset tonight: 7:42 pm
THREE-HOURLY DATA:
2pm 5pm 8pm
Temperature: 79 85 76
Relative Humidity: 36% 28% 40%
Surface Wind Direction: 010 010 350
Surface Wind Speed: 7 7 6
Transport Wind Direction: 010 010 010
Transport Wind Speed: 14 16 21
Estimated Mixing Height: 3500 4500 2200
Ventilation Index: 0 0 0
EXTENDED DISCUSSION:
Tomorrow looks line a near repeat of today with respect to transport winds. The latest
GFS model does indicate a slight shift to northwesterly late in the day, but likely not
enough to burn on.
The upper level low off the California coast opens up and drifts closer to the Pacific
Northwest on Thursday. This complicates the winds aloft pattern for western Oregon, but
models are indicating a good chance of some offshore or northeasterly flow for
unfavorable
burning conditions. Dry weather will continue Thursday and Friday and likely through the
weekend.
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:040912:1146
</pre>
</body>
</html>