JEFFERSON COUNTY FIELD-BURNING FORECAST
OREGON DEPARTMENT OF FORESTRY WEATHER OFFICE
9:30 AM PDT FRI SEP 29, 2023
*** Final Forecast of the
2023 Field-Burning Season ***
TODAY’S DISCUSSION:
An upper-level trough is gathering strength while moving SE and approaching the Oregon coast. Radar indicates showers in the area, and these will persist through the day. Poor mixing will result with light N winds and high humidity.
TODAY’S FORECAST:
Cloudy with periods of showers, about 0.10” of moisture possible. It will also cause cool conditions and poor mixing heights not reaching 2000 feet until late afternoon. Surface winds will be N 6-9 mph all day.
Madras’ Forecast High Today: 53°F (Thursday’s High: 64°F; Rainfall: .04”)
Transport Winds: N 6-9 mph through mid-afternoon; N 8-11 mph after 3 p.m.
Mixing Heights: Near 1200 feet late morning; 1500
feet at 2 p.m. and 2000 feet by 5 p.m.
Relative Humidity: 90% at 11 a.m.; lowering to 80% by 5 p.m.
EXTENDED DISCUSSION:
The upper trough will move SE into California and Nevada
for Saturday and Sunday. There is still
a chance of showers Saturday morning, but skies will clear with good mixing and
N winds by afternoon. Expect partly to
mostly sunny skies on Sunday and Monday, still cool but dry. Afternoon mixing will be good both afternoons
with N transport winds, NW by Monday.
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. Surface wind direction is the general expected wind direction.
at a specific point surface winds are highly dependent on local
terrain conditions.
4. Ventilation Index (if you want to calculate it) is the height of the
mixing layer times the transport wind speed divided by 1000.
This forecast is provided under an agreement between the Oregon Department of
Agriculture (ODA) and the Oregon Department of Forestry (ODF). For more information, contact ODA at 503-986-4701.
Gary Votaw
ODF Meteorologist