135
ACUS11 KWNS 211807
SWOMCD
SPC MCD 211807
MIZ000-INZ000-ILZ000-WIZ000-212000-
MESOSCALE DISCUSSION 0493
NWS STORM PREDICTION CENTER NORMAN OK
0107 PM CDT TUE APR 21 2026
AREAS AFFECTED...FAR SOUTHEAST WI INTO SOUTHWEST LOWER MI AND
NORTHERN PARTS OF IL AND IN
CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY
VALID 211807Z - 212000Z
PROBABILITY OF WATCH ISSUANCE...5 PERCENT
SUMMARY...ISOLATED OCCURRENCES OF HAIL APPROACHING SEVERE LEVELS
AND/OR LOCALLY STRONG WIND GUSTS ARE POSSIBLE WITH THE STRONGEST
STORMS THIS AFTERNOON. GIVEN THE MARGINAL NATURE OF THE ENVIRONMENT
AND EXPECTED STORM COVERAGE, A SEVERE THUNDERSTORM WATCH IS NOT
EXPECTED.
DISCUSSION...A SMALL CLUSTER OF ELEVATED THUNDERSTORMS HAS PERSISTED
INTO EARLY AFTERNOON IN SOUTHEAST WI, AIDED BY FORCING FOR ASCENT
ATTENDANT TO AN UPSTREAM SHORTWAVE TROUGH. 12Z OBSERVED AND MODEL
FORECAST SOUNDINGS SUGGEST THE ONGOING STORMS ARE ROOTED IN A MOIST
PLUME ATOP A CAPPING INVERSION AT THE BASE OF AN ELEVATED-MIXED
LAYER, WHICH HAS SPREAD EAST INTO THE REGION. TO THE SOUTH OF THE
ONGOING STORMS, STRONG DAYTIME HEATING COUPLED WITH A GRADUALLY
MOISTENING BOUNDARY LAYER FROM THE W/SW MAY ALLOW A SUBSET OF THE
ELEVATED CONVECTION TO BECOME PROGRESSIVELY MORE SURFACE-BASED
AMDIST A MARGINALLY UNSTABLE, BUT STEEP-LAPSE-RATE ENVIRONMENT.
ADDITIONAL, SURFACE-BASED STORMS ARE ALSO POSSIBLE IN 20-21Z TIME
FRAME ALONG A WEAK SURFACE FRONT ADVANCING SOUTHEAST THROUGH THE
REGION.
THE CURRENT MKX VWP INDICATES A LARGELY UNIDIRECTIONAL WIND PROFILE
YIELDING AROUND 30 KT OF EFFECTIVE BULK SHEAR. WIND PROFILES IMPROVE
WITH SOUTHWARD EXTENT ACROSS NORTHERN PART OF IL/IN OWING TO THE
PRESENCE OF A 35-40 KT LOW-LEVEL JET. MARGINALLY SEVERE HAIL APPEARS
TO BE THE PRIMARY HAZARD WITH THE ONGOING, ELEVATED STORMS.
COMPARATIVELY BETTER WIND POTENTIAL EXISTS WITH STORMS THAT CAN
BECOME SURFACE BASED ACROSS NORTHERN IL/IN WHERE THE STEEP LAPSE
RATES AND STRONGER LOW-LEVEL FLOW COINCIDE.
..MEAD.. 04/21/2026
..PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT
ATTN...WFO...IWX...GRR...LOT...MKX...
LAT...LON 41968946 42508910 42798814 42848655 42598553 42158528
41408538 41028589 40808680 40838779 41148858 41488902
41968946
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