453 
FXUS63 KUNR 191719
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
1119 AM MDT Tue Aug 19 2025

.KEY MESSAGES...

- An isolated storm or two can't be ruled out over the Black Hills
  today

- Drier and warmer conditions expected Tuesday and Wednesday.

- More seasonable temperatures and unsettled conditions return
  late in the week.

&&

.DISCUSSION...(Today Through Monday)
Issued at 150 AM MDT Tue Aug 19 2025

Current water vapor imagery and upper air analysis depicts 500hpa
ridge axis centered over the Rockies. At the sfc, broad high 
pressure sits centered over eastern CO. Aside from a few mid level
clouds over northeastern WY, skies over the CWA are mostly clear.
Temperatures are in the mid 60s to mid 70s with light and 
variable winds.
 
500hpa ridge will remain overhead today resulting in warmer and 
drier conditions. Low level upslope flow will continue to bring 
moisture into the western SD plains with afternoon dewpoints in 
the 50s to 60s. Steep lapse rates will support SB CAPE values of 
1000+ J/kg over the western SD plains by this afternoon. However, 
rising heights and warming 700hpa temps should keep conditions 
capped. An isolated storm or two can't be entirely ruled out over 
the eastern slopes of the Black Hills where upslope flow and 
terrain induced convergence may be enough to overcome the cap. 

Upper level ridge will take on a more positive tilt through the 
mid week with low level thermal ridge developing over the Northern
Plains. Wednesday should be the hottest day of the week as the 
low thermal ridge sets up over the CWA with highs in the 90s to 
low 100s. Not anticipating any need for heat headlines for 
Wednesday as drier air moves into the region. Thursday won't be 
quite as hot as Wednesday thanks to a northern stream trof grazing
the region and flattening out the ridge. Attendant cool front 
will sweep across the region late Thursday which will bring 
chances for showers/storms back to the region Thursday night. As 
the trof strengthens and digs into the eastern CONUS through the 
weekend, northwest flow will establish itself over the region. 
This translates to relatively cooler weather with daily chances 
for precip through the weekend.

&&

.AVIATION...(For the 18Z TAFS Through 18Z Wednesday)
Issued At 1119 AM MDT Tue Aug 19 2025

VFR conditions should prevail through most of the period. The
exception would be brief, localized MVFR conditions with any TSRA
that develop this afternoon (mainly over the Black Hills). Strong
south/southeast return flow will develop after 00z, and especially
after 03z. Low-level wind shear may become a concern in some
locations.

&&

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

$$

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