ACUS11 KWNS 261853
SWOMCD
SPC MCD 261852
KYZ000-INZ000-ILZ000-262115-

Mesoscale Discussion 1742
NWS Storm Prediction Center Norman OK
0152 PM CDT Sun Jul 26 2026

Areas affected...Illinois and portions of far southwest Indiana and
western Kentucky

Concerning...Severe potential...Watch possible

Valid 261852Z - 262115Z

Probability of Watch Issuance...60 percent

SUMMARY...Isolated convection is developing within a very unstable
air mass over southern IL, but it is unclear when a more pronounced
severe threat will emerge. Trends are being monitored, and watch
issuance will likely be needed by late afternoon, though timing
remains uncertain.

DISCUSSION...An isolated convective cell has recently developed
across south-central IL within a highly unstable air mass
(characterized by MLCAPE values of 4500-5000 J/kg based on the
recent 18 UTC DVN sounding). However, this cell is spatially
displaced from more focused low-level convergence/forcing for ascent
along a differential heating axis analyzed from western KY/southwest
IN into central and northern IL. Because of this (and based on
reflectivity trends over the past 20 minutes), it appears unlikely
that this cell will pose much of a severe threat.

Recent iterations of the RRFS actually seem to be capturing
convective trends well and depict this lone cell developing and
decaying within the next hour or so before additional convection
develops along the surface boundary and ahead of a subtle mid-level perturbation approaching from central IA during the 20-22 UTC
period. Recent GOES imagery shows gradual cumulus growth along the
boundary in southern IL as well as slow deepening of cumulus across
southeast IA/northeast MO, which lends credibility to the recent
RRFS solutions.

Additional convection developing later this afternoon will likely
fully realize the favorable thermodynamic and kinematic environment (characterized by SCP values of 8-12) draped across central IL into
the lower OH Valley. Guidance continues to depict relatively quick
upscale growth into an organized MCS by early evening with an
attendant threat for severe winds. Watch issuance will be needed
this afternoon/evening, but exact timing will depend on when more
widespread thunderstorm initiation becomes apparent.

..Moore/Leitman.. 07/26/2026

...Please see https://urldefense.com/v3/__http://www.spc.noaa.gov__;!!DZ3fjg!9SUe9PzTXLKpuw2ojFweaor7c8GRva0S9PAAJHXIQOo0bxOErR14z2-chXBjKIST8fyVLYNpJlrZnrKq31H3iNMddhw$ for graphic product...

ATTN...WFO...LMK...IND...PAH...ILX...LSX...DVN...

LAT...LON 37298772 37468862 37808921 39619054 40069075 40369065
40579034 40698988 40658934 40448890 40038844 39118771
38618735 37928681 37598670 37388682 37278713 37298772

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
* Origin: capitolcityonline.net * KY, USA (1:2320/107)