820
FXUS63 KUNR 291727
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
1127 AM MDT Sat Aug 29 2026

.KEY MESSAGES...

- Thunderstorms may develop over the area this afternoon and again
  Sunday afternoon. Some storms may become strong to severe and
  produce damaging wind gusts.

- Very warm weather with daily chances for afternoon storms
  continues into next week.

- Near-critical fire weather concerns continue into early next
  week, mainly over northeastern WY into southwestern SD.

&&

.DISCUSSION...(This Afternoon Through Friday)
Issued at 1105 AM MDT Sat Aug 29 2026

Upper level analysis depicts upper trof making its way onshore
into the PNW with broad ridging over the central US. The Northern
Plains sits under southwest flow with water vapor imaging showing
a few weak waves and convection over the Rockies. High based
storms capable of damaging wind gusts and hail are possible over
the area this afternoon as modest CAPE develops over the region.
This morning`s CAMs show some activity developing later this
afternoon and evening.

Stronger wave/upper low moves in for Sunday from the PNW and
grazes the CWA. Modest CAPE will once again fuel high based
convection over the CWA Sunday afternoon. Again, the main hazards
with any storms that develop will be damaging wind gusts and hail.
Low forecast confidence in storms developing as optimal forcing
and moisture will be located to the north and west of the CWA.

Broad ridging will continue over the central US with trof over
the western US. The CWA will sit under southwest flow, keeping
conditions warm (highs in the 80s to 90s) with near daily chances
for afternoon storms to close out the month. There are some fire
weather concerns for the end of this weekend into early next week,
mainly over northeastern WY into far southwestern SD. More
details in the fire weather discussion.

&&

.AVIATION...(For the 18Z TAFS Through 18Z Sunday)
Issued At 1123 AM MDT Sat Aug 29 2026

Another round of showers and isolated thunderstorms will be
possible later this afternoon into the early evening in
northeastern Wyoming and western South Dakota.

Storms are expected to start popping up around 21z/3pm in the
west and lasting through 05z/11pm east of Rapid City. Both KGCC
and KRAP may be impacted, so inherited PROB30s remained, only
minor adjustments to the timing were made.

Hail, frequent lightning, and gusty/erratic winds can be expected
with the stronger convective cores. Transient MVFR/IFR conditions
also possible around any heavier precipitation, mostly for vsby.
Outside of thunderstorms, SCT to BKN high-level clouds will
continue to stream across the region throughout the period, with
generally VFR conditions.

&&

.FIRE WEATHER...
Issued At 1105 AM MDT Sat Aug 29 2026

Near-critical to locally critical fire weather conditions may
form over Weston County into southwestern SD on Sunday afternoon.
Breezy westerly winds will develop by the afternoon with sustained
winds of 20 to 25 mph, gusting to 35 to 40 mph. Meanwhile
afternoon RHs will range from 15 to 20%. At this time, will hold
off on issuing any fire weather headlines due to low confidence in
coverage and duration of any critical fire weather conditions.

Fire weather concerns will continue into early next week as hot
and mostly dry conditions continue across the area. Main areas of
concern will be over northeastern WY into southwestern SD where
afternoon humidities will drop into the teens to low 20s.

&&

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

$$

DISCUSSION...Wong
AVIATION...GS
FIRE WEATHER...Wong