FXUS63 KUNR 261710

AFDUNR



Area Forecast Discussion For Western SD and Northeastern WY

National Weather Service Rapid City SD

1110 AM MDT Thu Jun 26 2025



.KEY MESSAGES...



- Less active weather expected today, though 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...(Today Through Wednesday)

Issued at 142 AM MDT Thu Jun 26 2025



Water vapor imagery tonight shows an upper-level wave shifting from 

the Rockies onto the High Plains. Ahead of this wave, a corridor of 

enhanced deep moisture extends from near the west coast of Mexico 

northward through the north central U.S., supporting strengthening 

convection across the central Plains. Earlier thunderstorm activity 

over western SD is largely weakening at this hour as it continues to 

shift eastward, though lingering showers with occasional lightning 

strikes persist over central SD. In the wake of the shower/storm 

activity, nighttime microphysics RGB imagery and obs/webcams show 

developing low stratus/fog over the western/central Dakotas into far 

eastern WY. This activity will likely expand through the overnight 

and early morning hours, with some areas of dense fog not out of the 

question. Will continue to monitor and evaluate the need for any fog-

related headlines.



Midlevel shortwave trof shifts east of the area early today, with 

shortwave ridging arriving in its stead. Height rises thru 18-21z 

should limit early afternoon convection. However, terrain-driven 

convergence in a general absence of large-scale drivers of flow 

along with CAPE ~1000 J/kg may support some spotty storms 

predominantly over the Black Hills. Aside from isolated storms, a 

warm and mostly dry day is in store. High temperatures may be 

trending a smidge milder, with some locations across our eastern 

tier and over the Black Hills likely (EPS/GEPS probabilities 70% or 

greater) remaining in the 70s. Later in the afternoon/evening, 

height falls will likely support additional convection over higher 

terrain features to our west in MT/WY, as suggested by most members 

of the 00z HREF. A subset of members carry some thunderstorms 

associated with this activity into portions of northeastern WY and 

northwestern SD late tomorrow evening through the overnight, 

potentially aided by increasing 850 mb flow and attendant 

frontogenesis/theta-E advection. Increasing MUCAPE (HREF mean 

approaching 1000 J/kg) and marginal deep-layer shear (25-30 kt) 

could support storm organization and potentially a sneaky, 

localized, conditional severe threat. 



The next midlevel shortwave and attendant surface trof cross the 

region Friday. Timing of the surface trof will be critical to 

potential of thunderstorms, particularly any severe chances, across 

our area. For now, given a rather early trof passage over 

northeastern WY/far western SD, the best convective environment 

featuring SBCAPE in excess of 2 kJ/kg and deep-layer shear of 30-40 

kt looks to set up east of the Black Hills Friday afternoon. This 

placement is also consistent with the primary zone of integrated 

vapor transport per the latest GFS/ECWMF deterministic models 

coupled with the potential for a pseudo-dryline mixing eastward off 

of higher terrain toward the Badlands. Fat CAPE profiles, relatively 

weak low-level shear (but decent low-level hodograph curvature), and 

deep, well-mixed boundary layers should favor large hail 

(potentially significant) and damaging winds as the primary hazards. 

Outside of the storms, and particularly west of the aforementioned 

pseudo-dryline, hot and dry conditions will be the story, with highs 

climbing into the 90s.



Hotter temperatures shift eastward toward central SD on Saturday as 

a lobe of the low-level thermal ridge pivots eastward and a weak 

baroclinic zone sinks into the area. Zonal midlevel flow carries 

another shortwave/corridor of Q-vector convergence toward the region 

very late Saturday through Sunday, which may support multiple rounds 

of convection atop the lingering baroclinic zone. Behind this 

disturbance, relatively high confidence in a southeast-to-northwest 

oriented ridge building early next 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 18Z TAFS Through 18Z Friday)

Issued At 1109 AM MDT Thu Jun 26 2025



Isolated showers and storms are possible after 18-19z this

afternoon, mainly around the Black Hills where transient MVFR

conditions will be possible in any heavier showers.



Otherwise, VFR conditions are expected through the forecast 

period.



&&



.UNR WATCHES/WARNINGS/ADVISORIES...

SD...None.

WY...None.

&&



$$



DISCUSSION/KEY MESSAGES...Sherburn

AVIATION...SE

