[willamette-fcst] Field Burning Forecast - July 17, 2017

[Willamette Valley Field Burning Forecast]

SILVERTON HILLS FIELD BURNING FORECAST
OREGON DEPARTMENT OF FORESTRY WEATHER OFFICE
8:45 AM PDT MON JUL 17, 2017

BURN ADVISORY:

Agricultural burning is not recommended.

Prep burning is not allowed.

WEATHER DISCUSSION:

A dry disturbance aloft approaches Oregon and will disrupt onshore flow at the surface in the Willamette Valley. Gradients are almost flat currently, but the timing of this incoming disturbance is the limiting factor today for possible field burning ahead of a marine push.

TODAY'S FORECAST:

Mostly Sunny becoming Partly Cloudy this afternoon.

Salem's high temperature today will be near 83°F (average is 83°F).
Relative humidity:  Dropping below 60% by 10:30 a.m. and to near 34% by 5 p.m.
Surface winds: N 7-12 mph this morning; shifting N-NW 10-15 mph this afternoon.
Transport winds: N 5-10 mph this morning; NW 10-15 mph this afternoon.
Mixing height: Rising to 3000 feet around 10 a.m. and to 4500 feet by 2 p.m.
Salem's sunset tonight: 8:54 p.m.

(Salem Airport data for Sunday, July 16th: High 77°F; Rainfall: .00")
(Maximum Ventilation Index expected today: 68)

EXTENDED DISCUSSION:

Unsettled weather persists through the week for the Silverton Hills, as a disturbance over the Pacific Ocean pushes weak fronts into Oregon. Marine cloud cover will move into the Willamette Valley during evenings and linger through late morning on both Tuesday and Wednesday. The disturbance gathers moisture by Wednesday night and moves across the Willamette Valley Thursday morning with wetting rains near 0.25 inches before mid-day. The influx of cooler marine air this week keeps temperatures below seasonal averages.

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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