ACUS11 KWNS 010346
SWOMCD
SPC MCD 010346=20
IAZ000-NEZ000-MNZ000-SDZ000-010545-

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.=20

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 https://urldefense.com/v3/__http://www.spc.noaa.gov__;!!DZ3fj= g!7YJ-YjtMcDboQkyxkuTcZTUz20MSrC4zUXHfShrosigowwkFuEm3L-VoYW8o1SQy8mml7woPM= z17Kic3J0KHJQEnLeA$ 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=20

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


=3D =3D =3D
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