[willamette-fcst] Field Burning Forecast - July 12, 2017

[Willamette Valley Field Burning Forecast]

SILVERTON HILLS FIELD BURNING FORECAST
OREGON DEPARTMENT OF FORESTRY WEATHER OFFICE
8:45 AM PDT WED JUL 12, 2017

BURN ADVISORY:

Recommended times for agricultural burning are from 9 a.m. until 7 p.m.

Prep burning is not allowed.

WEATHER DISCUSSION:

Ridging aloft supporting high pressure over the Silverton Hills begins to break down today as a disturbance forms out over the Pacific Ocean. Mixing improves quickly under clear skies and July sunshine, and NW transport winds increase ahead of the afternoon sea breeze arriving.

TODAY'S FORECAST:

Clear skies becoming Partly Cloudy this afternoon

Salem's high temperature today will be near 83°F (average is 82°F).
Relative humidity:  Dropping below 60% by 9 a.m. and nearing 30% by 5 p.m.
Surface winds: N at 5-10 mph becoming NW at 8-12 mph after 4 p.m.
Transport winds: NW 5-10 mph becoming W-NW 10-15 mph after 12 p.m.
Mixing height: Above 3000 feet by 9 a.m. and increasing to 5000 feet by 1 p.m.
Salem's sunset tonight: 8:57 p.m.

(Salem Airport data for Tuesday, July 11th: High 82°F; Rainfall: .00")
(Maximum Ventilation Index expected today: 75)

EXTENDED DISCUSSION:

There will be few changes to the weather pattern moving into the weekend. Temperatures will glide back down below seasonal averages as onshore flow slowly builds Thursday and again on Saturday. Weak disturbances over the Pacific Ocean will move through on Thursday and Saturday as well, enhancing the afternoon sea breeze with W-NW transport winds, and helping gradients stack favorably for smoke evacuation & dispersion.


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

Tom Jenkins, AEM
ODF Meteorologist
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