107
FXUS63 KUNR 161032
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
432 AM MDT Wed Sep 16 2026

.KEY MESSAGES...

- Elevated fire weather conditions expected Wednesday afternoon
  across northeast WY

- Unsettled weather pattern will bring better precipitation
  chances from Thursday into the weekend

&&

.DISCUSSION...(Tonight Through Tuesday)
Issued at 948 PM MDT Tue Sep 15 2026

04Z upper level analysis has weak ridging across the northern and
central Plains with sharp trof digging across the Pacific
Northwest. Weak shortwave is currently lifting northeast across
south central WY, with some light shower and thunderstorm activity
noted. Skies are currently partly cloudy across the forecast
area. At the surface, high pressure is in place across the eastern
Dakotas, with a weak low pressure center over central Wyoming. In
between these two surface features, light southeast return flow
is underway - with wind speeds mainly in the 10-15 mph range.
Temperatures across the forecast area at 10pm are mainly in the
50s to lower 60s.

Weak shortwave across south central Wyoming will continue to lift
northeast into the forecast area after midnight. Some isolated
light rain showers and some isolated thunder are expected from the
Black Hills area and east through the early morning hours.
Southeast boundary layer flow may become a bit breezy after
midnight, subsiding a bit by early Wednesday morning. Low
temperatures are expected to dip into the upper 40s to mid 50s by
sunrise.

For Wednesday...upper shortwave will shift east of the area by mid
morning, with skies clearing across much of the area by mid day. A
weak frontal boundary will slide through western areas by late
morning and early afternoon, switching light southerly winds
around to out of the north. Thermal ridge rebounds across the
area late in the day, allowing temperatures to climb into the
upper 70s to mid 80s by late in the afternoon. Increasing clouds
ahead of the next weather system will keep temperatures mild
Wednesday night.

Strong upper low develops in the western trof across the West
Coast region on Thursday, with Northern Plains ridge axis
shifting east during the day. A strong upper shortwave is progged
to lift through the forecast area during peak heating late
Thursday afternoon into Thursday evening. With modest east to
southeast surface return flow bringing moisture back into the area
during the day, and decent low level shear, there could be a few
stronger storms that develop across far southwestern portions of
the area. These showers and storms should continue to shift
northeast across the area during the late afternoon and evening
hours, with best chances for significant rainfall across
southwest into south central South Dakota into Thursday night.
Many locations across this area could see a quarter to half an
inch of precipitation from these showers and storms, with locally
higher amounts possible. With ample cloud cover and precip across
much of the area, temperatures will be cooler, in the 60s to mid
70s on Thursday.

Closed upper low shifts into the Northern Rockies on Friday, with
weak ridging moving back into the forecast area. Friday will be
mostly dry, with temperatures rebounding into the 70s. By Friday
night and for the weekend, the upper level low will traverse the
Northern Plains, bringing widespread light moisture, and cooler
temperatures to the area. If this pattern and track of the upper
low holds true, many locations could see an additional quarter to
half an inch of precipitation through early Monday.

Mainly dry and mild conditions return for the first half of next
week.

&&

.AVIATION...(For the 12Z TAFS Through 12Z Thursday Morning)
Issued At 428 AM MDT Wed Sep 16 2026

VFR conditions are expected through the TAF period. Winds will
shift to the north through this morning and become breezy. Gusts
of 25-30KT expected over the western SD plains.

&&

.FIRE WEATHER...
Issued At 1056 PM MDT Tue Sep 15 2026

Elevated fire weather conditions return Wednesday as warmer
temperatures (upper 70s to mid 80s), breezy winds, and RH values
in the low to mid 20s return to northeast WY. Conditions improve
Thursday as cooler temperatures, higher RH values, and a chance
for precipitation return to the area.

&&

.UNR WATCHES/WARNINGS/ADVISORIES...
SD...None.
WY...None.
&&

$$

DISCUSSION...15
AVIATION...Wong
FIRE WEATHER...15