ACUS11 KWNS 212354
SWOMCD
SPC MCD 212353=20
KYZ000-INZ000-ILZ000-MOZ000-220130-

Mesoscale Discussion 1237
NWS Storm Prediction Center Norman OK
0653 PM CDT Sun Jun 21 2026

Areas affected...southern Illinois into southern and central Indiana

Concerning...Tornado Watch 363...365...

Valid 212353Z - 220130Z

The severe weather threat for Tornado Watch 363, 365 continues.

SUMMARY...The tornado threat continues across Tornado Watches #363
and #365.

DISCUSSION...Supercells with a history of producing tornadoes are
ongoing across Tornado Watches #363 and #365 this evening. The
overall environment remains very favorable for thunderstorm
rotation, with effective-layer shear on the order of 40-50 knots and
0-3 kilometer SRH ranging from 400 m2/s2 from the Evansville, IN,
VAD to over 600 m2/s2 from the Indianapolis, IN, VAD.=20

Likely contributing to this enhanced low-level helicity is a strong
easterly component to the low-level wind field in response to an MCV
tracking northeast into central Indiana. As this MCV moves northeast
toward Indianapolis, increasing low-level theta-e to the south and
east of the MCV should be sufficient to offset the loss of diurnal
heating to maintain sufficient instability into the evening hours,
particularly across the watch area. Thus, the threat for
thunderstorms will continue. The threat for tornadoes will exist as
long as ongoing thunderstorms can remain sufficiently rooted in the
boundary layer to ingest these helicity-rich low-level air parcels.

As storms move east of I65, low-level theta-e quickly drops off and
storms should become increasingly elevated. As this occurs, the
overall tornado threat should lessen and a transition to strong,
damaging winds may occur before thunderstorms weaken.

..Marsh.. 06/21/2026

...Please see https://urldefense.com/v3/__http://www.spc.noaa.gov__;!!DZ3fj= g!_wv_OJmocId1V8CKySzP88LinS61vZcrVQAh4CVK3lOzUFl-5mXI2vH1u5tJWzqmT4XAg8qHW= LaPK7Go0KJ-2jjOC5E$ for graphic product...

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

LAT...LON 38599018 39518828 39848672 39738536 38728522 38098731
37678889 37799007 38599018=20

MOST PROBABLE PEAK TORNADO INTENSITY...100-125 MPH
MOST PROBABLE PEAK WIND GUST...65-80 MPH
MOST PROBABLE PEAK HAIL SIZE...UP TO 1.25 IN


=3D =3D =3D
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