ACUS01 KWNS 021957
SWODY1
SPC AC 021956

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0256 PM CDT Thu Apr 02 2026

Valid 022000Z - 031200Z

...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS OVER PARTS OF
EASTERN IOWA...NORTHERN ILLINOIS...AND SOUTHERN WISCONSIN...

...SUMMARY...
Severe thunderstorms capable of producing a few tornadoes remain
probable across parts of eastern Iowa, northern Illinois, and
southern Wisconsin this afternoon and evening. Additionally,
damaging thunderstorm winds will be possible from eastern Iowa
northeast into Michigan.

...20z Update IA, IL, MO and southern WI...

Rapid air mass modification is underway to the south of a warm front
lifting northward across the western Great Lakes and upper Midwest.
Clearing beneath the advancing mid-level dry slot may allow
temperatures to warm into the low 70s, with surface dewpoints near
60 F. This will support weak buoyancy amid very strong shear
profiles (0-1 km SRH >300 m2/s2) from observed VADs and regional RAOBs.

Scattered thunderstorms and supercells ongoing over northern MO and
southern IA should mature and present a severe hazard over much of
the ENH area as they spread northeastward through this evening. A
few tornadoes (some strong and fast moving), hail and damaging gusts
are expected. Additional storms may develop within the warm conveyor
belt farther east across IL this afternoon/evening. Upscale growth
into one or more clusters with damaging gusts and a couple tornadoes
is the primary concern.

The main change with the 20z update was to trim thunderstorm and
severe probabilities to the west of the advancing cold front. See
the prior discussion for more information.

..Lyons.. 04/02/2026

.PREV DISCUSSION... /ISSUED 1113 AM CDT Thu Apr 02 2026/

...IA/IL/MO/WI...

Morning water vapor imagery shows a strong shortwave trough over
northeast KS, with an associated mid-level jet and dry-slot rotating
around the base of the trough into western MO. A deep surface low
currently south of OMA will track northeastward across IA this
afternoon, with a tight gradient of low-level moisture and
instability along the track of the low. Very strong low-level shear
and sufficient CAPE in the warm sector will pose a risk of
fast-moving supercells capable of damaging winds, tornadoes
(possibly strong), and hail. The area of greatest concern is over
eastern IA into northern IL and far southern WI. Perhaps the
biggest forecast uncertainty is the widespread cloud cover and
limited diurnal destabilization, but the approaching dry slot may
compensate by mid-afternoon and allow a period of afternoon heating.

The coverage of storms with southward extent is uncertain across
eastern MO and central/southern IL. Recent CAM solutions continue
to show only widely scattered discrete development across this
corridor. However, given the forecast of strong low-level shear and
favorable synoptic forcing, those storms that do form would pose a
risk of damaging winds and a few tornadoes.

...Eastern IL/IN/Lower MI...

Strong southerly low-level winds will maintain 60s dewpoints across
eastern IL/western IN, and result in the warm front lifting
northward into southern Lower MI by this evening. This will provide
a favorable environment for a few severe storms capable of damaging
winds and perhaps a few tornadoes.

$$


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