[willamette-fcst] Silverton Hills Midday Forecast_Pete.doc
Willamette Valley Field Burning Forecast
willamette-fcst at listsmart.osl.state.or.us
Mon Jul 25 11:55:44 PDT 2016
SILVERTON HILLS FIELD BURNING FORECAST
OREGON DEPARTMENT OF FORESTRY WEATHER OFFICE
11:55 AM PDT MON JUL 25, 2016
BURN ADVISORY:
Agricultural burning is not recommended.
Prep burning is allowed from now until 1 p.m. with a 50 acre limit.
WEATHER DISCUSSION:
A dry upper-level trough initiated a weak marine push into western Oregon this morning. Patchy low clouds penetrated into mainly the extreme northern and southern Willamette Valley this morning but have mostly dissipated.
This afternoon appears to be the best opportunity for open burning this week. Minor negative gradient stacking will need to be reversed by daytime heating, and onshore flow will need to continue at modest intensity. The first PIBAL is scheduled for 1 p.m.
TODAY'S FORECAST:
Sunny and slightly cooler.
Salem's high temperature today will be near 86°F (average is 84°F).
Relative humidity: Dropping to near 35% by 5 p.m.
Surface winds: NW 5-10 mph.
Transport winds: NW 10-18 mph.
Mixing height: Rising to 4500 feet by 5 p.m.
Salem's sunset tonight: 8:46 p.m.
(Salem Airport data for Sunday, July 24th: High 89°F; Rainfall: .00")
(Maximum Ventilation Index expected today: 80)
EXTENDED DISCUSSION:
A building upper-level ridge will bring a warming trend through the week with temperatures climbing into the low-to-mid 90s Thursday and Friday. Transport winds will turn mostly northerly. A cool-down is expected this weekend with a series of upper-level troughs providing better burning potential next week.
The National Weather Service's digital forecast is available at:
http://forecast.weather.gov/MapClick.php?lat=44.90549606158295&lon=-122.8106689453125&site=pqr&unit=0&lg=en&FcstType=text
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 15 mph.
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 (ft) times
the transport wind speed (mph) 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 (ODA) and the Oregon Department of Forestry (ODF). For
information contact ODA at 503-986-4701.
To add/remove your email address from this list, please go to:
http://listsmart.osl.state.or.us/mailman/listinfo/willamette-fcst
Pete Parsons
ODF Meteorologist
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