Storm Prediction Center Mesoscale Discussion 1159

   Mesoscale Discussion 1159
   NWS Storm Prediction Center Norman OK
   1128 PM CDT Tue Jun 16 2026

   Areas affected...east-central and southeast SD...far southwest
   MN...northwest IA

   Concerning...Severe potential...Watch unlikely 

   Valid 170428Z - 170630Z

   Probability of Watch Issuance...20 percent

   SUMMARY...Isolated hail/wind potential increasing with southeast
   extent and during the 05-08z (12am-3am CDT) period.

   DISCUSSION...A lobe of upper-level forcing for ascent associated
   with an approaching upper jet streak will continue to rapidly move
   east-southeast from the MT/Dakotas border and across the Dakotas
   tonight.  As this occurs, strengthening low-level warm-air advection
   to the north (immediate cool side) of a west-northwest to
   east-southeast oriented frontal zone (analyzed from western SD into
   southeast SD) will act to destabilize the airmass over parts of the
   mid MO Valley tonight.  Forecast soundings over central SD (valid
   currently at 04z) show scant buoyancy amidst strong deep-layer shear
   and elongated hodographs.  RAP forecast soundings near Sioux City,
   IA over the next few hours show moisture increasing in the 900-800
   mb layer as the terminus of a LLJ focuses over the region.  As a
   result, elevated parcels will attain much greater buoyancy (e.g.,
   less than 100 J/kg to 2500 J/kg MUCAPE) through 08z.  It is
   plausible as both the elevated instability and forcing for ascent
   develop and overspread parts of southeast SD into adjacent portions
   of MN/IA, that intensification of ongoing storms moving southeast
   will occur or additional storms will develop and strengthen. 
   Although some uncertainty remains regarding the evolution of storm
   activity, at least an isolated risk for large hail and severe gusts
   may develop tonight and become increasingly possible with time
   (i.e., 05 to 08 UTC).

   ..Smith/Gleason.. 06/17/2026

   ...Please see www.spc.noaa.gov for graphic product...

   ATTN...WFO...MPX...DMX...FSD...ABR...

   LAT...LON   43849910 44169922 44539889 44699854 43749482 43259462
               42649505 42449558 43849910 

   MOST PROBABLE PEAK WIND GUST...55-70 MPH
   MOST PROBABLE PEAK HAIL SIZE...UP TO 1.25 IN