532
FXUS63 KUNR 132329
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
529 PM MDT Thu Aug 13 2026

.KEY MESSAGES...

- An active pattern will bring unsettled conditions at least
  through the weekend, with daily chances for thunderstorms.

- Temperatures will generally be near average through the end of
  the week into early next week.

&&

.DISCUSSION...(This Evening Through Thursday)
Issued at 208 PM MDT Thu Aug 13 2026

Water vapor imagery shows broad upper ridging centered across south
SE CONUS with the main axis stretching through the Midwest. Moist,
active southwesterly flow continues across the western CONUS...all
the way back to a trough near the West Coast. Several shortwaves
are crossing northern High Plains to the central/northern
Rockies. The nearest wave is pushing through central/eastern WY
through the NE WY zones south into the CYS CWA. As the wave
continues NE, showers and thunderstorms will push further into
western SD while weakening. Weak CAPE and shear will damper any
severe weather potential today. The next (much stronger) wave will
bring continued chances of elevated convection late this evening
and into the overnight hours. These showers could generally
produce up to half an inch of QPF by 12z. Active weather will
continue through Friday with additional shortwaves bringing
mid-level forcing. Models show a surface low strengthening
tomorrow near the ND/MT line with a cold front pushing through NE
WY and far western SD. Good Theta E advection across NW/Central
SD ahead of the front will support SBCAPE nearing 2000 J/kg. While
shear is not impressive, could still see pulsing isolated
strong/severe storms Friday afternoon and early evening, with
large hail as the main threat. Active weather and near average
temperatures will continue through weekend into the first half of
next week, with daily chances for showers and thunderstorms.

&&

.AVIATION...(For the 00Z TAFS Through 00Z Friday Evening)
Issued At 528 PM MDT Thu Aug 13 2026

Scattered showers will be possible across western SD for the
remainder of today into tonight, with thunderstorms possible this
afternoon and through the overnight hours for northeast WY. MVFR
to IFR conditions are expected tonight across the area as moist
southeast upslope flow continues. Fog may develop overnight across
the Black Hills and areas south of I-90 before burning off Friday
morning.

&&

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

$$

DISCUSSION...13
AVIATION...Dye