SILVERTON HILLS FIELD BURNING FORECAST
OREGON DEPARTMENT OF FORESTRY WEATHER OFFICE
11:45 AM PDT THU AUG 22, 2019
BURN ADVISORY:
Recommend agricultural burning be limited to the hours between 8 a.m. and 6 p.m. today.
Prep burning is not allowed.
WEATHER DISCUSSION:
Skies continue to open up over the Silverton Hills, allowing the atmosphere to begin warming up and drying out. Northerly winds remain steady with onshore gradients remaining negatively-stacked; while some improvement in gradients is expected, northerly flow will do little more than promote drying in the fields east of Salem.
TODAY’S FORECAST:
Mostly Cloudy becoming Partly Cloudy later.
Salem's high temperature today will be near 73°F (average is 82°F).
Relative humidity: Below 60% now and dropping below 40% by 5 p.m.
Surface winds: N 7-12 mph all day.
Transport winds: N 10-15 mph all day.
Mixing height: Near 5,000 feet now and remaining at or above 5,000 feet through 6 p.m.
Salem’s sunset tonight: 8:07 p.m.
(Salem Airport data for Wednesday, August 21st: High 71°F; Rainfall: .06”)
(Maximum Ventilation Index expected today: 75)
EXTENDED DISCUSSION:
Friday will see the atmosphere under generally westerly flow aloft, continuing to bring cooler air in from the Pacific Ocean. Northerly winds should moderate a bit to become more NW with an afternoon sea breeze, with partly cloudy skies giving a chance for additional drying to take place. Saturday and Sunday will see this onshore flow steadily build, with weak disturbances rolling along the Canadian border. This will keep the atmosphere cooler than seasonal averages, with fair mixing each day, as an upper-level ridge slowly forms out over the Pacific Ocean.
Monday appears to offer the next day of favorable field burning conditions, with W-NW flow aloft enhancing onshore gradients with a stronger sea breeze in the afternoon. Temperatures are expected to return to seasonal averages in the low 80’s, as well.
The National Weather Service’s digital forecast is available at:
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.
5. In accordance with OAR 837-110-0090, all field
burning shall be
banned when any two of the following criteria are present:
A. Temperature of 95 degrees Fahrenheit or above
B. Relative humidity of 30 percent or below
C. Wind speed of 15 miles per hour or higher
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.
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Tom Jenkins, AEM
ODF Meteorologist