616
FXUS63 KUNR 190445
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
1045 PM MDT Fri Jul 18 2025

.KEY MESSAGES...

- Daily chances for thunderstorms through early next week.

- Temperatures around or above normal expected through the
  forecast period.

&&

.DISCUSSION...(This Evening Through Friday)
Issued at 149 PM MDT Fri Jul 18 2025

Current surface analysis shows low pressure centered over central
SD, with frontal boundary running through south central SD into
western NE and central WY. Upper models show zonal flow aloft.
Temperatures currently sit in the upper 70s and 80s with
relatively light northwest to northeast winds behind the boundary.

This afternoon, boundary wraps up into northeastern WY, providing
an area of forcing amid a strong cap today. If storms are able to
fire up, expected over northeastern WY down into southwestern SD
late this afternoon or early evening. Modest shear but plenty of
CAPE could support an organized severe storm or two if initiation
is able to occur. Likely wont see any development outside of the
immediate frontal zone. Threat today would be large hail and
strong winds. Shortwave moving across the FA will support
elevated showers/storms overnight, however no organized severe is
expected.

Models show zonal to quasi-zonal flow persisting through the
forecast period, with disturbances marking daily chances for
storms over the area. While widespread severe is not expected,
localized strong storms will remain a possibility over the
weekend. Shortwave moves though at a better time Saturday to
support isolated severe storm potential, coupled with 1000-2000
j/Kg ML CAPE and 30-40 kt 0-6km shear, if able to overcome the
cap. May see potential for terrain driven upslope Black Hills
development moving off into the plains. Similar set up for Sunday
will support more isolated storm potential. Longer range models
show little change in the overall pattern, keeping temperatures
relatively steady, with daily (but limited) convective activity.

&&

.AVIATION...(For the 06Z TAFS Through 06Z Saturday Night)
Issued At 1041 PM MDT Fri Jul 18 2025

Areas of -RA with some embedded TS can be expected across both
terminals. Added a PROB30 group at the KRAP terminal from 10-12z,
with prevailing TS -RA at the KGCC terminal through 09z.
Conditions will improve across the KGCC through the morning but
there is chance for some MVFR/IFR CIGS to impact the KRAP terminal
around 15z. VFR conditions will prevail at both terminals by 18z,
but PROB30 groups have been added to both terminals to account for
late afternoon and early evening convective chances.

&&

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

$$

DISCUSSION/KEY MESSAGES...Dye
AVIATION...Woodward