[willamette-fcst] Silverton Hills Forecast - Wed, Jul 28 2010
Willamette Valley Ag/Burning Forecast
willamette-fcst at listsmart.osl.state.or.us
Wed Jul 28 11:55:33 PDT 2010
SILVERTON HILLS FIELD BURNING FORECAST
OREGON DEPARTMENT OF FORESTRY WEATHER OFFICE
12:00 PM PDT WED JUL 28 2010
BURN ADVISORY:
Agricultural burning burning is not recommended.
Prep burning is not allowed.
Propane flaming is allowed from 12:00pm to 5:00pm.
WEATHER DISCUSSION:
Upper level trough remains off the coast today ever so slowly moving eastward.
Thundershowers are moving through central Oregon in the last few hours. This is keeping
pressure gradients flat between Salem and Redmond with hazy conditions east of Salem.
However models show more westerly flow developing during the afternoon. Will need pibals
to confirm this. Low clouds have burned off in the valley with middle and higher clouds
remaining.
Expect middle and high clouds to remain somewhat throughout the day.
Thus temperatures will be a little cooler than yesterday with the high temperatures today
in the low to mid 80s. With slightly cooler temperatures and some cloud cover,
humidities
will be somewhat higher. Humidity will drop below 50 percent by 1 to 2 p.m. with a
minimum around 42 percent around 5 p.m. Wind flow will be light through the early
afternoon, gradually showing a tendency toward west to northwest later this afternoon as
the inland temperatures warm up. With thunderstorms likely developing over the Cascades
and not a big increase in onshore pressure gradients, burning conditions are still
questionable for later this afternoon.
Sunset tonight: 8:38 pm
THREE-HOURLY DATA:
2pm 5pm 8pm
Temperature: 78 83 75
Relative Humidity: 48% 42% 46%
Surface Wind Direction: 310 290 270
Surface Wind Speed: 6 8 8
Transport Wind Direction: 300 300 290
Transport Wind Speed: 5 8 11
Estimated Mixing Height: 3000 4000 1000
Ventilation Index: 18 32 11
EXTENDED DISCUSSION:
Upper level low will gradually move eastward through the remainder of the week and
weekend. Thunderstorm threat will continue over the Cascades through Friday but as the
low approaches, thunderstorms should move eastward and allow surface pressure gradients
to
increase, giving an improved chance for open burning on Friday. Eventually the trough
moves to the east over the weekend and gives way to northwesterly flow aloft early next
week. Temperatures will continue to cool toward the weekend with marine low clouds
likely
moving in over the weekend.
EXTENDED FORECAST:
Thursday: Mostly sunny, with a high near 82. Calm wind becoming north between 4
and 7 mph.
Thursday Night: Partly cloudy, with a low around 51. North wind around 6 mph
becoming calm.
Friday: Mostly sunny, with a high near 82. Calm wind becoming north northwest
around 6 mph.
Friday Night: Mostly cloudy, with a low around 50.
Saturday: Mostly sunny, with a high near 76.
Saturday Night: Partly cloudy, with a low around 52.
Sunday: Mostly sunny, with a high near 78.
Sunday Night: Mostly cloudy, with a low around 52.
Monday: Mostly sunny, with a high near 82.
Monday Night: Partly cloudy, with a low around 52.
Tuesday: Mostly sunny, with a high near 84.
Notes:
1. Mixing height, as used here, is the lowest height at which the
potential temperature exceeds the 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.
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