ACUS02 KWNS 290558
SWODY2
SPC AC 290556

Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1256 AM CDT Sun Mar 29 2026

Valid 301200Z - 311200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS THE UPPER
MISSISSIPPI RIVER VALLEY INTO THE GREAT LAKES REGION...

...SUMMARY...
Isolated strong to severe thunderstorms are possible across portions
of the upper Mississippi River Valley to Lower Michigan late Monday
night into early Tuesday morning.

...Synopsis...
A low-amplitude upper wave is forecast to progress along the
U.S./Canadian border Monday through early Tuesday morning. Ahead of
this wave, a surface cyclone will steadily intensify across the
Plains as it migrates towards the upper MS Valley. Northward
moisture return over the next 48 hours ahead of the surface low will
likely result in mid to upper 50 dewpoints reaching the upper MS
Valley and Great Lakes region by early evening. Concurrently,
westerly flow aloft will advect 7-8 C/km lapse rates eastward
towards the Great Lakes region. This combination of low-level
moistening and steepening lapse rates aloft will yield a buoyant air
mass within the warm conveyor region of the developing cyclone.

Capping and mostly dry low-level conditions will preclude
thunderstorm development during the day. After 00 UTC, a
strengthening of the low-level jet will augment low-level moistening
and isentropic ascent between 925-850 mb across the upper MS Valley
and Great Lakes region. Thunderstorm development is expected between
the 03-06 UTC period across northeast IA into southern WI/northern
IL along the warm frontal zone. Westerly effective bulk shear values
on the order of 30-40 knots will likely support storm organization,
including the potential for elevated supercells initially, with an
attendant large hail risk. With time, storm motions along the zonal
frontal zone will promote upscale growth into one or more clusters
as convection spreads east into MI. Some damaging wind threat may
materialize with this activity depending on its proximity to the
surface warm front.

A more isolated hail threat appears likely across northern lower MI
after 06 UTC as more focused isentropic ascent spreads north.
Although convection will be elevated, elongated hodographs through
the CAPE-bearing layer will promote organized cells with mainly a
large hail threat.

..Moore.. 03/29/2026

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