950
FXUS63 KUNR 301130
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
530 AM MDT Tue Jun 30 2026

.KEY MESSAGES...

- Isolated severe storms are possible over south central SD late
  tonight. Main hazards will be large hail and damaging winds.

- Unsettled weather continues through the rest of the week with
  near daily chances for isolated afternoon showers/storms and
  temperatures in the 80s to 90s.

&&

.UPDATE...
Issued at 1041 PM MDT Mon Jun 29 2026

Wind Advisory and Red Flag Warning were allowed to expire as
scheduled this evening, and no major changes were made to the
forecast with this evening`s update. Next chance of showers and a
few thunderstorms still looks to hold off until after 5-6 PM
Tuesday evening starting along the Nebraska border. Tuesday will
still be breezy and dry with near-critical fire weather conditions
in roughly the same corridor as today`s Red Flag Warning
(northeast WY south of Gillette and Newcastle into southwestern
SD and the Badlands), but winds will be lower and much more
marginal. Will continue to monitor any trends.

&&

.DISCUSSION...(This Evening Through Monday)
Issued at 112 PM MDT Mon Jun 29 2026

Current upper level analysis depicts upper low centered over MT
with 90-100KT 300 mb jet streak over WY/CO. Water vapor imagery
shows dry air streaming into western SD ahead of another weak wave
associated with the aforementioned jet streak. Most areas will
remain dry today though isolated to scattered showers/storms are
possible over northwestern SD this afternoon and evening as the
jet streak moves overhead. Ample deep layer shear of 50+KT will
support rotating updrafts and organized severe weather, though
forecast ML CAPE values will be 500-1000 J/kg which will limit
overall severe threat. Still, we could see a couple of stronger to
severe storms with large hail and damaging wind gusts as the main
hazards. Southwest winds are picking up across the region with
gusts of up to 50-55 mph in WY. These winds will move over western
SD later this afternoon, a Wind Advisory remains in effect for
much of the western SD plains.

Unstable southwest flow continues across the Northern Plains
through Tuesday with another shortwave approaching the region late
Tuesday into early Wednesday. This should bring another round of
convection to our corner of the plains late Tuesday night/early
Wednesday morning. In terms of severe threat, some elevated
instability could push into our south central zones late Tuesday
evening with forecast MU CAPE approaching 3000+ J/kg. Deep layer
shear will be marginal (around 20-30 kt) so not expecting any
widespread organized severe weather but we could see isolated
elevated storms capable of large hail and damaging winds.

Storm chances continue through Wednesday as a weak wave
approaches the region. Again, the higher instability will be
displaced to the south of our CWA but forecast ML CAPE of
1000-1500 J/kg and 40-50kt of deep layer shear may be enough to
support an isolated severe threat Wednesday afternoon and evening.
Looking into the holiday weekend, models are still indicating
warming temperatures through the end of this week with highs in
the upper 80s to 90s by Friday. Continued southwest flow across
the Northern Plains will support near daily chances for afternoon
storms as upper level disturbances ripple along the flow.

&&

.AVIATION...(For the 12Z TAFS Through 12Z Wednesday Morning)
Issued At 526 AM MDT Tue Jun 30 2026

VFR conditions are expected through the forecast period. Isolated
to scattered thunderstorms will develop across the area this
evening and persist through Tuesday night. MVFR/IFR conditions
will be possible in the stronger storms. Breezy winds are expected
today across northwestern South Dakota with gusts to 35 kt.

&&

.FIRE WEATHER...
Issued At 112 PM MDT Mon Jun 29 2026

Humidities over Southern Campbell County into southwestern SD
have dropped into the teens to low 20s with increasing southwest
winds. Widespread critical fire weather conditions expected this
afternoon across those areas as humidities drop to around 15 to
18% and southwest winds gust up to 55 mph. Elsewhere, elevated to
near-critical fire weather conditions expected to develop this
afternoon.

Elevated to near-critical fire weather conditions expected again
tomorrow as humidities drop to 15 to 20% across much of the area.
Lighter winds will preclude the development of critical fire
weather conditions, though localized critical fire weather
conditions may develop over northwestern SD where westerly winds
may gust up to 40 mph.

Daily elevated to near-critical fire weather conditions
anticipated through the latter half of the week, especially over
northeastern WY into southwestern SD as temperatures climb into
the 90s and humidities drop into the teens to low 20s.

&&

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

$$

UPDATE...KSmith
DISCUSSION...Wong
AVIATION...13
FIRE WEATHER...Wong