076
FXUS63 KUNR 181720
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
1120 AM MDT Mon Aug 18 2025

.KEY MESSAGES...

- Slight risk (2/5) for severe thunderstorms today across much of
  western SD

- Turning hot and dry Tuesday through Thursday. Could see upper
  90s to 100F by Wednesday and Thursday.

- Turning cooler with unsettled weather returning by next weekend.

&&

.DISCUSSION...(Today Through Sunday)
Issued at 338 AM MDT Mon Aug 18 2025

Current satellite and radar imagery show scattered storms
associated with a weak upper level wave across southeastern
MT/southwestern ND/northwestern SD. These storms should graze far
northwestern SD through the early morning hours. While some of the
stronger updrafts may produce small hail and gusty winds, not
anticipating any severe weather at this time.

Main concern today will be the potential for strong to severe
thunderstorms across the western SD plains this afternoon evening.
Continued moist, upslope flow and steep mid-level lapse rates of
~8.0C/km will support a moderately unstable airmass (ML CAPE of
2000+J/kg) over much of western SD. Meanwhile, bulk shear values
of 30-40kt will support organized convection. The limiting factor
is the lack of large scale ascent which may keep widespread
convection from occurring and should keep the threat conditional.
The most likely spots for storms this afternoon will be around
the eastern slopes of the Black Hills where terrain induced
convergence will be enough to overcome the cap. Some CAMs have
also been showing a signal for scattered storms developing over
the western SD plains along a sfc trof.

500hpa ridge will strengthen over the western CONUS through the
mid week, resulting in warmer and drier conditions by Tuesday.
Wednesday and Thursday look to be the hottest days of the week
with temperatures approaching 100F. Northern stream trof/upper low
grazes the region late Thursday with attendant cold front
bringing cooler temperatures to the region for Friday into the
weekend. Unsettled northwest flow establishes itself over the
Northern Plains for the weekend as well, with daily chances for
precip returning to the region.

&&

.AVIATION...(For the 18Z TAFS Through 18Z Tuesday)
Issued At 1120 AM MDT Mon Aug 18 2025

VFR conditions are expected through much of the period. The
exception will be in any SHRA/TSRA this afternoon and evening,
which could bring localized MVFR/IFR conditions along with hail
and strong, erratic wind gusts.

&&

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

$$

DISCUSSION/KEY MESSAGES...Wong
AVIATION...Sherburn