[willamette-fcst] Silverton Hills AM Forecast_Gary.doc
Willamette Valley Field Burning Forecast
willamette-fcst at listsmart.osl.state.or.us
Wed Sep 7 08:44:44 PDT 2016
SILVERTON HILLS FIELD BURNING FORECAST
OREGON DEPARTMENT OF FORESTRY WEATHER OFFICE
8:45 AM PDT WED SEPT 7, 2016
BURN ADVISORY:
Agricultural burning is allowed from 2:00 p.m. until 5:30 p.m.
Prep burning is not allowed.
WEATHER DISCUSSION:
Moist NW flow will cause clouds to slowly dissipate today while fields may still be wet from rain. The rain occurred early on Tuesday which averaged a quarter to a half inch on those fields. Very weak transport winds will become WNW in the afternoon but still under 10 mph. Pressure gradients are currently negatively stacked with only a chance of balancing today. Gradients and the wet fields are the primary negative factors for burning potential today.
Cloudy becoming partly sunny by mid-afternoon.
Salem's high temperature today will be near 76°F (average is 79°F).
Relative humidity: Falling below 60% by 2:00 p.m., to a low of 45% around 5:00 p.m.
Surface winds: WNW 4-6 mph becoming NNW 6-9 mph around 2:00 p.m.
Transport winds: WNW 3-5 mph increasing to 6-10 mph in mid-afternoon.
Mixing height: Rising to 2000 feet by 11:00 a.m. and 4000 feet about 2:00 p.m.
Salem's sunset tonight: 7:37 p.m.
(Salem Airport data for Tuesday, September 6th: High 72°F; Rainfall: .11")
(Maximum Ventilation Index expected today: 50)
EXTENDED DISCUSSION:
No more rain is expected this week but transport winds are expected to turn N in the valley on Thursday and then weak ridging will turn it NNE on Friday. Burning conditions still look marginal over the weekend and early next week with mostly N winds though other aspects look better. We will remain dry with good mixing potential each day.
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
Gary Votaw
ODF Meteorologist
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