ACUS11 KWNS 212354

SWOMCD

SPC MCD 212353 

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. 



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 www.spc.noaa.gov for graphic product...



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



LAT...LON   38599018 39518828 39848672 39738536 38728522 38098731

            37678889 37799007 38599018 



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