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SILVERTON HILLS FIELD BURNING FORECAST
OREGON DEPARTMENT OF FORESTRY WEATHER OFFICE
12:00 PM PDT MON JUL 09 2012
BURN ADVISORY:
Recommended burn times for agricultural burning are from now until 7:00pm.
Prep burning is is allowed from now until 5:00pm.
Propane flaming is allowed from now until 5:00pm.
WEATHER DISCUSSION:
Weather maps show a typical summertime weather pattern for the Pacific Northwest this
morning. A thermal trough extends from the central valley of California into southwest
Oregon. A lee-side trough extends from near Wenatchee, Washington into central Oregon.
Satellite pictures show marine clouds penetrating coastal valleys this morning and even a
few patches of low clouds in parts of the Willamette Valley. Convection has already
begun east of the Cascades in parts of central and NE Oregon and thunderstorms are likely
again today in those regions.
The Salem sounding showed a very slight cooling sinceyesterday morning, but the
atmosphere is quite stable all the way to about 6500 feet abovethe surface. The high
temperature today should be down a few degrees from yesterday but aforecast high of 85
should push afternoon mixing heights to above 3500 feet. Slight gradient stacking will
likely continue through the afternoon making for unfavorable open
field burning conditions.
TODAY'S FORECAST:
Sunny and warm.
Salem's high temperature today will be near 85.
Minimum relative humidity today: 36%.
Surface winds: Northerly 4-6 becoming northwesterly 7-10 late.
Transport winds: Northerly to northwesterly 6-10 increasing late.
Maximum mixing height: 3600 feet.
Sunset tonight: 8:59 pm
THREE-HOURLY DATA:
2pm 5pm 8pm
Temperature: 84 85 82
Relative Humidity: 55% 55% 54%
Surface Wind Direction: 360 340 300
Surface Wind Speed: 5 7 9
Transport Wind Direction: 330 320 320
Transport Wind Speed: 6 10 14
Estimated Mixing Height: 2800 3000 1000
Ventilation Index: 17 30 14
EXTENDED DISCUSSION:
Upper level flow will remain southwesterly for the next few days. Dry weather continues
through mid week. Low level transports will likely be an unfavorable northerly through
Wednesday as well. An upper level trough will be approaching from the west Wednesday
night and Thursday. Models have been inconsistent with timing and intensity, but
precipitation chances increase Thursday and Friday.
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:090712:1149
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