[willamette-fcst] Field Burning Forecast - August 8, 2017

[Willamette Valley Field Burning Forecast]

SILVERTON HILLS FIELD BURNING FORECAST
OREGON DEPARTMENT OF FORESTRY WEATHER OFFICE
8:45 AM PDT TUE AUG 8, 2017

BURN ADVISORY:

Agricultural burning is not recommended.

Prep burning is not allowed.

WEATHER DISCUSSION:

Very similar conditions to Monday, but slightly warmer under clear skies. The upper-level ridge has anchored in place near the NW Oregon coast, and will limit mixing today as offshore flow develops. Remnant smoke from regional wildfires and afternoon haze will be the only factors to limit heating, allowing late afternoon temperatures to approach 95°F; humidity will be closely monitored for potential State Fire Marshal conditions later today.

TODAY'S FORECAST:

Mostly Clear with Smoke & Haze.

Salem's high temperature today will be near 95°F (average is 84°F).
Relative humidity:  Below 60% by 10:30 a.m. and nearing 30% by 5 p.m.
Surface winds: Variable 5 mph or less this morning, becoming N 5-10 mph this afternoon.
Transport winds: N 5-10 mph this morning, becoming N-NE 5-10 mph this afternoon.
Mixing height: Rising to 3000 feet by 5 p.m.
Salem's sunset tonight: 8:28 p.m.

(Salem Airport data for Monday, August 7th: High 93°F; Rainfall: .00")
(Maximum Ventilation Index expected today: 30)

EXTENDED DISCUSSION:

Little change in the weather pattern for the remainder of the week. The upper-level ridge will slowly strengthen over NW Oregon, further limiting mixing conditions as the atmosphere continues to warm & dry out. The offshore flow increases and will also draw more regional wildfire smoke into the Willamette Valley from across the Cascades. Poor mixing and degraded air quality will persist, along with the above-average temperatures for early August, through Friday, when the upper-level ridge begins to weaken and shift east towards the Cascades. Onshore flow will redevelop this weekend as a disturbance over the Pacific approaches, bringing cooler air and more favorable conditions for field burning mid-month.

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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