ACUS11 KWNS 122134
SWOMCD
SPC MCD 122133
KYZ000-INZ000-ILZ000-MOZ000-122330-

Mesoscale Discussion 1958
NWS Storm Prediction Center Norman OK
0433 PM CDT Wed Aug 12 2026

Areas affected...Eastern Missouri into the lower Ohio River Valley

Concerning...Severe Thunderstorm Watch 577...

Valid 122133Z - 122330Z

The severe weather threat for Severe Thunderstorm Watch 577
continues.

SUMMARY...Severe thunderstorms will continue to pose a severe wind
and hail threat for the next hour or two, but should become
increasingly sporadic through the evening hours. Downstream watch
issuance will most likely not be required.

DISCUSSION...The remnants of an MCS continue to push southward
across the lower OH Valley, and although storm mode has become
increasingly disorganized and outflow-dominant (likely a consequence
of diminishing deep-layer wind shear with southward extent),
lightning counts have increased over the past 20 minutes within a
few cells from eastern MO into far southwest IN. This uptick in
intensity comes as convection begins to push into a regional
buoyancy maximum where MLCAPE was recently analyzed to be around
3500 J/kg. Consequently, the potential for large hail (most likely
around one inch) and strong/severe downburst winds should linger for
the next 1-2 hours as convection migrates through the best
thermodynamic environment.

However, regional reflectivity/velocity imagery shows that much of
this activity is quickly becoming displaced behind a coherent
convective outflow and/or has storm motions into the cold pool.
Weaker deep-layer wind shear with southward extent should maintain
the outflow-dominant nature of the convection and will eventually
promote storm weakening and an increasingly isolated severe threat
heading into the mid/late evening. Latest HRRR/RRFS time-lagged
guidance captures this trend well and suggests the severe threat may
not extend much beyond the southern bounds of WW 577. While
convective trends will continue to be monitored as storms push
through the buoyancy maximum, downstream watch issuance is currently
not anticipated.

..Moore.. 08/12/2026

...Please see https://urldefense.com/v3/__http://www.spc.noaa.gov__;!!DZ3fjg!5yAnAy7XyffhdtNqH9JUyeadBAkgB2Di6uRLp7dEqPX-6HiS4U-aOTfwB9dPuh96yBiHgZHgb1B0d-tdA0UsKhwle8I$ for graphic product...

ATTN...WFO...ILN...LMK...PAH...LSX...

LAT...LON 39249129 39119068 38508854 38308798 38258739 38288658
38408591 38598501 38698461 38718427 38588405 38378397
38108412 37808448 37418501 37138549 36858595 36768634
36728676 36718730 36778790 36858841 36988909 37228976
37459026 37749081 38019124 38249156 38529182 38719193
39129174 39249129

MOST PROBABLE PEAK TORNADO INTENSITY...UP TO 90 MPH
MOST PROBABLE PEAK WIND GUST...55-70 MPH
MOST PROBABLE PEAK HAIL SIZE...UP TO 1.25 IN


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--- scorpsmtpd
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