ACUS11 KWNS 042329
SWOMCD
SPC MCD 042329=20
INZ000-ILZ000-MOZ000-050200-

Mesoscale Discussion 0640
NWS Storm Prediction Center Norman OK
0629 PM CDT Mon May 04 2026

Areas affected...South-central Illinois and Southern Indiana

Concerning...Severe potential...Watch possible=20

Valid 042329Z - 050200Z

Probability of Watch Issuance...40 percent

SUMMARY...An isolated severe threat for large hail is expected to
continue for a few hours across south-central Illinois, and may
affect southern Indiana. The for weather watch issuance is
uncertain.

DISCUSSION...A couple cells have recently develop to the northeast
of the St. Louis metro. The activity is located along the eastern
edge of a pocket of moderate instability, where the RAP has MLCAPE
around 1000 J/kg. The storms are being supported by an area of
low-level convergence and by large-scale ascent associated with a
subtle shortwave trough, evident on water vapor imagery. The WSR-88D
VWP near St Louis has effective shear in the 30 to 40 knot range,
and the RAP shows very steep mid-level lapse rates exceeding 7.5
C/km. This should be favorable for large hail with supercells that
form. However, a capping inversion is evident over much of
southeastern Illinois and southern Indiana. Also, RAP suggests that
instability is very weak in this same area. For this reason, the
storms are expected to remain elevated, and the eastern extent of
the severe threat is uncertain.

..Broyles/Hart.. 05/04/2026

...Please see https://urldefense.com/v3/__http://www.spc.noaa.gov__;!!DZ3fj= g!5e3zTTb04j4anW2xHd66nhvzUFBhha1Crc1lql6SGFpY_qVUz9HnGdSEodb3gLEU-vb4nCRKO= 7dJndBEprb_eL6AWYo$ for graphic product...

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

LAT...LON 38058802 38218956 38489008 38859021 39299012 39638974
39798899 39748736 39618654 39338617 38828613 38318631
38088688 38058802=20

MOST PROBABLE PEAK WIND GUST...UP TO 60 MPH
MOST PROBABLE PEAK HAIL SIZE...1.00-1.75 IN


=3D =3D =3D
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