438
FXUS63 KUNR 191712
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
1112 AM MDT Wed Aug 19 2026

.KEY MESSAGES...

- Showers and storms continue into the overnight hours.

- More chances for afternoon storms on Wednesday, mainly across
  western SD.

- Trending warmer to end the week into next weekend.

&&

.UPDATE...
Issued at 1016 PM MDT Tue Aug 18 2026

Current radar has widespread showers/storms over the forecast area
this evening, with some wind gusts near 50 mph around storms.
Precipitation will continue overnight, moving out from west to
east early Wednesday morning.

Forecast remains mostly on track. Have removed PoP mention during
the day Wednesday. Models are all pointing to us being dry, and
CAMs show nothing during the afternoon/evening. It`s not
impossible, but more likely most places will remain dry once the
overnight showers/storms move out. Things then look mostly dry the
remainder of the week as ridge dominates the northern plains. Next
significant disturbance looks to move through the area Sunday.

&&

.DISCUSSION...(This Evening Through Tuesday)
Issued at 1242 PM MDT Tue Aug 18 2026

Shortwave will push through region today and bring another round of
storms to the CWA this afternoon. Modestly unstable airmass of 1500-
2000 J/kg MUCAPE will develop over western SD by this afternoon and
evening. The instability combined with 40-50kt bulk shear will
support organized convection and potential severe weather. Main
hazards will be strong wind gusts (some gusts could exceed 70 mph)
and large hail. There is still uncertainty as to the timing and
coverage of convection this afternoon, though right now it looks
like the most likely area for severe storms stretches from
northeastern WY into portions of western and south central SD.

Wednesday is looking drier as rising heights courtesy of the
building ridge to our west will limit convection. We could still see
some isolated storms towards the eastern third of our CWA where 1000-
1500 J/kg MUCAPE will develop by the afternoon.

The upper level pattern shifts after Wednesday as aforementioned
ridge continues to build over the western US and overspreads the
region. Our CWA will sit on the northeastern periphery of the ridge,
meaning we`ll see warmer temps and continued chances for storms
through the end of the week.

&&

.AVIATION...(For the 18Z TAFS Through 18Z Thursday)
Issued At 1111 AM MDT Wed Aug 19 2026

VFR conditions are expected through the TAF period.

&&

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

$$

UPDATE...Dye
DISCUSSION...Wong
AVIATION...Schultz