302
FXUS63 KUNR 170438
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
1038 PM MDT Mon Jun 16 2025

.KEY MESSAGES...

- Slight risk (2 of 5) for severe thunderstorms later this
  afternoon/evening
- Marginal risk (1 of 5) for severe thunderstorms Tuesday
  afternoon/evening in the south
- Becoming hot and dry Wednesday through Saturday

&&

.DISCUSSION...(This Evening Through Monday)
Issued at 222 PM MDT Mon Jun 16 2025

20z surface analysis had cold front from far western MN to the NE
panhandle, snaking northwestward into north-central WY, merging
with lee trough. Water vapour loop had west/southwest flow over
the northern plains with an embedded shortwave over western WY
evidenced by cirrus increase over northern WY and bubbling
convection over central MT. 18z KUNR sounding depicted robust
MLCIN. SPC mesoanalysis had 100-300J/kg MLCIN east of the Black
Hills and 50-100J/kg to the west. 0.5km visible satellite imagery
show CU confined to the higher terrain of the Black Hills and
those aren`t too robust, yet. Erosion of CIN will be key to
forecast through this evening.

Later this afternoon/evening, shortwave scoots east/northeast.
SPC HREF indicates 1-2KJ/kg MUCAPE develops by evening with local
2-3KJ/kg amounts in/near aforementioned frontal boundary. Most
CAMs break cap with increasing convection over northeastern WY
22-00z and then into western SD in the evening. If surface-based
convection struggles, elevated CAPE will be fuel for effective
bulk shear from 40-50kts. If surface-based convection occurs,
robust supercells with 2"+ hail possible from northeastern WY into
far southwestern SD. One wild card is how much cirrus shield
ahead of wave will suppress heating. Confidence is high for
thunderstorms, but medium for severity. Overnight, showers/TS will
continue and weaken. Temperatures will be near guidance.

Tuesday, secondary shortwave trough slips through the CWA with
increasing chances for shra/TS. CAPE/shear profiles point toward
the southern third of the CWA for a marginal (1 of 5) risk of
severe thunderstorms. Temperatures will be near guidance in the
north with the potential for below guidance in the south where
highest PoPs are painted. PWATs ~125% of normal should fuel
beneficial QPF for some folks.

Wednesday through Saturday, upper/thermal ridge builds into the
northern Plains in response to deepening upper trough over the
northwestern CONUS. Hot and dry weather foreseen. EFI eventually
hits 70-80th percentile for MaxT which translates to some toasty
90s starting Thursday.

&&

.AVIATION...(For the 06Z TAFS Through 06Z Tuesday Night)
Issued At 1036 PM MDT Mon Jun 16 2025

Clusters of showers and a few thunderstorms will continue in the
forecast area for the overnight hours. Any thunderstorm may
contain strong gusty erratic winds and hail as well as locally
IFR conditions. Showers/isolated thunderstorms will continue
Tuesday morning. Outside of storms, VFR conditions will prevail.

&&

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

$$

DISCUSSION/KEY MESSAGES...Helgeson
AVIATION...Dye