629
FXUS63 KUNR 250450
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
1050 PM MDT Fri Jul 24 2026

.KEY MESSAGES...

- Very hot and dry weather expected for this weekend with highs
  exceeding 100F across much of the area. Heat indices over south
  central SD will exceed 105F Saturday and Sunday.

- Thunderstorms will be possible at times this weekend into next
  week. Widespread severe weather not expected but storms could
  produce gusty winds.

- Critical fire weather conditions Sat with high based dry
  thunderstorms possible along with low RH and dry fuels

&&

.UPDATE...
Issued at 1024 PM MDT Fri Jul 24 2026

HI values of 105+ expected over south central SD for tomorrow and
Sunday, with overnight lows in those areas dropping to only 75F
for Saturday night into Sunday morning. Therefore have opted to
upgrade Heat Advisory to an Extreme Heat Warning for those area
from 1 pm CDT Saturday afternoon through 9 pm CDT Sunday evening.

UPDATE Issued at 958 PM MDT Fri Jul 24 2026

Forecast remains on track for a very hot and unsettled weekend with
highs in the 100s across much of the area Saturday and Sunday. The
daily record high for Downtown Rapid City for tomorrow (July 25) is
105. With highs in Rapid City forecast to be 105 we could easily
match or exceed the daily record tomorrow. 107 is the all time high
temperature record for Downtown Rapid City and while we might not
quite make it there tomorrow, it will definitely be very hot in our
corner of the Northern Plains for the next couple of days. Further
east in our south central counties, HI values could reach 105+F
Saturday afternoon.

In addition to the heat, it`s still looking like a weak upper
wave will ride the upper ridge and impact the CWA Saturday
afternoon. Storms expected to develop over northeastern WY by noon
Saturday with storm coverage increasing over much of western SD
by 2/3 PM. Storms will persist into the evening hours. While
widespread organized severe weather isn`t anticipated, inverted V
soundings indicate high based storms with strong wind gust
potential and we could see a few 60+ mph gusts in some of the
stronger cells tomorrow afternoon.

&&

.DISCUSSION...(This Evening Through Friday)
Issued at 1221 PM MDT Fri Jul 24 2026

Upper level ridge over the Rockies will shift east and expand
over the central CONUS. This will result in very hot temperatures
this weekend into next week. Batches of mid level monsoon moisture
will advect through the region as near daily waves eject out of
the Rockies and into the FA. Upper level wave and trailing sfc
trough now progressing across North Dakota and MT. This system may
support a few isolated showers or storms across NW SD in the
afternoon, continued a low pop for this. A separate weak impulse
may also support a shower or storm across northeast WY in the
evening , but the chances for any convection making it into the FA
are very slim and have left pops out. Main item of concern will
be the large ridge of high pressure that will build into the
region. Upper ridge will shift east Sat with very hot temps
expected. Highs will reach 100 or higher for most locations on the
Plains, supporting adv level heat index readings. Low level
moisture will deplete some with mixing, but sustained southerly
flow will prevent the BL from drying out too much most places.
This will help keep heat index readings higher, esp over central
SD. Heat looks to persist most of next week although highs will
trend more toward the mid and upper 90s as opposed to the 100s
like this weekend. Have issued a heat adv through Sunday when the
core of he heat is expected. The adv will be marginal out in
northeast WY where very dry BL conds and slightly lower temps will
keep heat index values in the 95 to 100 range. In addition to the
heat, expect near daily TS chances as monsoon moisture advects
around the NW side of the ridge. This includes Sat when a stronger
monsoon wave will advect around the ridge in SW flow and into the
FA, supporting high based TS chances. Gusty winds will be
possible with any thunderstorms in this period given very high
based nature and resultant inverted-V profiles per drying BL. Sct
wind gusts over 50 mph (likely higher in stronger cells) will be
possible give DCAPE of 1500-2000 J/KG. Not much rain expected with
these cells, which will support critical fire weather conds when
coupled with dry fuels and low RH. Ridge will retrograde back west
some by mid next week, supporting slightly cooler but still hot
temps, with isold-sct TS chances continuing as the lee trough
interacts will passing impulses.

&&

.AVIATION...(For the 06Z TAFS Through 06Z Saturday Night)
Issued At 1046 PM MDT Fri Jul 24 2026

Mainly VFR conditions are expected through the forecast period.
The exception will be the possibility of isolated high based
thunderstorms with gusty winds initially building over northeast
Wyoming and the Black Hills by early Saturday afternoon, then
spreading onto the adjacent plains into the evening hours.

&&

.FIRE WEATHER...
Issued At 1221 PM MDT Fri Jul 24 2026

Very hot temperatures return this weekend and will persist into
next week as a ridge of high pressure builds over the region. This
will support elevated to critical fire weather conditions as RH`s
drop into the teens on the Plains each day. Winds will be
marginal most days, except for perhaps far Western SD Sunday when
gusts to 30 will be possible. Poor recovery can also be expected
most nights across portions of northeast WY, the Black Hills, and
far western SD given warm overnight lows. In addition, there will
be near daily chances for isolated thunderstorms as batches of mid
level monsoon moisture push through the region. Storms may
produce very little rainfall and gusty winds, supporting a dry
lightning threat at times. This is especially the case Saturday
afternoon and evening across northeast WY and western SD. TS`s
will produce very little rainfall and gusty/erratic winds. Wind
gusts over 50 mph will be possible with any cells, potentially
higher. Given high potential for dry TS, min RH`s of 15 to 20
percent, very dry fuels, and gusty erratic winds have issued a red
flag warning for Sat.

&&

.UNR WATCHES/WARNINGS/ADVISORIES...
SD...Heat Advisory from noon Saturday to 8 PM MDT Sunday for SDZ001-
     002-012>014-025>027-030>032-041>044-072>078.
     Red Flag Warning from noon Saturday to midnight MDT Saturday
     night for SDZ319>333.
     Extreme Heat Warning from 1 PM Saturday to 9 PM CDT Sunday for
     SDZ046-047-049.
WY...Heat Advisory from noon Saturday to 8 PM MDT Sunday for
     WYZ054>056-058>060.
     Red Flag Warning from noon Saturday to midnight MDT Saturday
     night for WYZ314>318.
&&

$$

UPDATE...Wong
DISCUSSION...JC
AVIATION...15
FIRE WEATHER...JC