<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 MON JUL 16 2012
BURN ADVISORY:
Recommended burn times for agricultural burning are from now until 7:00pm.
Prep burning is not allowed.
Propane flaming is allowed from now until 5:00pm.
WEATHER DISCUSSION:
An upper level low has been drifting southward along the Oregon coast this morning and is
now centered just offshore of Waldport, Oregon.
As the upper low drifts south and west today, counter-clockwise flow around the low will
turn transport winds an unfavorable northeasterly. Transport wind speeds will be light.
Surface pressure gradients are weakly onshore and afternoon surface winds will be light
northwesterly.
As surface temperatures warm this afternoon there is a chance for additional showers to
develop. Over the Cascades those showers could become thunderstorms and with the
northeasterly transport flow there is a slight chance that a thunderstorm could drift
into the Valley. Winds near those storms would be variable in direction and gusty.
THIS AFTERNOON'S FORECAST:
Mostly cloudy to partly sunny with a chance for showers or a slight chance of a
thunderstorm.
Salem's high temperature today will be near 77.
Relative humidity drops to 50% by 3pm. Minimum relative humidity 42%.
Surface winds: Light northwesterly.
Transport winds: Light northeasterly.
Maximum mixing height: 8000 feet.
Sunset tonight: 8:55 pm
THREE-HOURLY DATA:
2pm 5pm 8pm
Temperature: 73 78 78
Relative Humidity: 50% 40% 47%
Surface Wind Direction: 020 010 020
Surface Wind Speed: 6 7 5
Transport Wind Direction: 000 290 290
Transport Wind Speed: 3 4 3
Estimated Mixing Height: 7000 8000 8000
Ventilation Index: 21 32 24
EXTENDED DISCUSSION:
The upper low will continue to provide a threat for thunderstorms on Tuesday. In
addition transport winds are likely to have an unfavorable easterly component.
The upper low pushes east of the region late Wednesday or early Thursday, but the chance
for showers and thunderstorms will continue through mid week. Longer range charts
indicate the potential for another upper disturbance dropping southward into the
region on Thursday for a continued slight chance of showers and slightly below average
temperatures.
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:160712:1157
</pre>
</body>
</html>