Mesoscale Discussion 0928 NWS Storm Prediction Center Norman OK 1046 PM CDT Sun May 31 2026 Areas affected...Portions of the Missouri River Valley Concerning...Severe Thunderstorm Watch 257...259... Valid 010346Z - 010545Z The severe weather threat for Severe Thunderstorm Watch 257, 259 continues. SUMMARY...The severe threat is gradually waning across far southeast South Dakota/northwest Iowa as storms continue to grow upscale. Further south, trends continue to be monitored for robust convective initiation, though confidence in storm coverage is limited. DISCUSSION...Local radar imagery from KFSD shows continued upscale growth of initially semi-discrete supercells into a more consolidated convective band. GOES IR imagery also shows the onset of a weakening trend as cloud-top temperatures begin to warm. New cell development continues on the southern flank of the band; however, the onset of nocturnal stabilization is evident in regional web cams and by modifying the 00 UTC OAX RAOB to local surface observations. Increasing inhibition will likely begin to modulate the potential for further cell development heading later into the evening hours (especially in the absence of stronger forcing for ascent). Consequently, it appears likely that the recent weakening trend and the overall severe threat will continue to wane. Further south, convection appears to be struggling against the aforementioned nocturnal stabilization as weak thunderstorms continue to dissipate within an hour or so after initiation. Percolating congestus is noted in GOES IR imagery west of I-29 and north of I-80 along the surface trough/dryline, and recent RRFS solutions hint at more robust initiation in this region by around 06 UTC. Given the favorable kinematic environment sampled by the 00 UTC OAX sounding, severe thunderstorms remain possible if deep convection can become established. However, given the lack of appreciable forcing for ascent and increasing inhibition, these RRFS solutions appear bullish. ..Moore.. 06/01/2026 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...DMX...FSD...OAX... LAT...LON 40639584 40529610 40519643 40639683 40709704 40859722 41029735 42359693 43329658 43519631 43469530 43259514 42899504 42449500 42029511 41129558 40639584 MOST PROBABLE PEAK TORNADO INTENSITY...UP TO 90 MPH MOST PROBABLE PEAK WIND GUST...55-70 MPH MOST PROBABLE PEAK HAIL SIZE...1.00-1.75 IN
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