FXUS63 KUNR 262251

AFDUNR



Area Forecast Discussion For Western SD and Northeastern WY

National Weather Service Rapid City SD

451 PM MDT Thu Jun 26 2025



.KEY MESSAGES...



- There is a chance for a few afternoon/evening storms over and

  near the Black Hills



- There is a slight risk (level 2 of 5) for severe thunderstorms

  Friday afternoon, mainly east of the Black Hills. Main hazards

  will be large hail (quarter size or larger) and damaging wind

  gusts.



- Very warm to hot on Friday and Saturday, with highs climbing

  into the 90s for most.



&&



.DISCUSSION...(This Evening Through Thursday)

Issued at 153 PM MDT Thu Jun 26 2025



Current visible satellite imagery shows clear skies over much of 

the CWA with CU developing over the Black Hills and portions of

northeastern WY. Most recent mesoscale analysis depicts 1000-2000

J/kg SB CAPE over the Black Hills into northwestern SD and 

portions of northeastern WY. Lack of large scale forcing will 

limit convective activity today though terrain influence 

convergence may provide enough lift for isolated storms to form 

over the Black Hills this afternoon. Height falls ahead of an 

approaching shortwave trough could support additional convection 

over WY/MT, mainly over the higher terrain. Most recent CAMs show 

convection over northeastern WY by 21-22z with potentially another

round of convection later tonight as an LLJ develops over western

SD into northeastern WY. Deep layer shear will be marginal at 

20-30kt, which, when combined with 1000-1500 J/kg MUCAPE could 

support a localized, conditional severe threat overnight.



The shortwave and attendant surface trof crosses the region 

tomorrow. Thunderstorm and severe wx risk will depend on timing of

the sfc trof. Most recent NAM runs have been fairly consistent in

the trough pushing eastward across northeastern WY and far 

western SD tomorrow morning, which will favor thunderstorms 

developing east of the Black Hills tomorrow afternoon. Low level 

southerly flow ahead of the sfc trof will advect moisture into the

western SD plains with sfc DPs reaching into the upper 50s to low

60s. This will support corridor of moderate to strong instability

(SB CAPE in excess of 2000 J/kg) across northwestern into south 

central SD through the afternoon hours. 30-40kt shear, Fat CAPE 

profiles, and steep low to mid-level lapse rates will favor a 

large hail and damaging wind threat. Temperatures tomorrow 

afternoon will climb into the 90s with very dry air west of the 

sfc trof.



Another hot day on tap for Saturday as low level thermal ridge 

noses back into the region. Highs will once again climb into the 

90s, especially east of the Black Hills. Weak baroclinic zone will

sink into the northwestern portions of the CWA by the afternoon 

hours. Low-level frontogenesis may support convection Saturday 

afternoon into the overnight hours. Baroclinic zone should be 

south of the CWA by Sunday, with highs slightly cooler (in the low

to mid 80s). Looking into next week, relatively high confidence 

in a southeast-to- northwest oriented ridge building early in the 

week, which will bring warmer temperatures but may favor at least 

some isolated/scattered thunderstorms through at least the first 

half of the week.



&&



.AVIATION...(For the 00Z TAFS Through 00Z Friday Evening)

Issued At 449 PM MDT Thu Jun 26 2025



Isolated showers and storms will be possible through evening

across northeast WY and far NW SD. There is a very small chance

for another round of ISOLD showers/storms late this evening and

overnight as a weak impulse traverses the region.



Otherwise, VFR conditions are expected through the forecast 

period.



&&



.UNR WATCHES/WARNINGS/ADVISORIES...

SD...None.

WY...None.

&&



$$



DISCUSSION/KEY MESSAGES...Wong

AVIATION...JC

