Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1241 AM CDT Mon Mar 30 2026
Valid 301200Z - 311200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE UPPER MISSISSIPPI VALLEY...
...SUMMARY...
A few severe thunderstorms with large hail, are expected across
parts of the upper Mississippi River Valley late tonight into early
Tuesday morning. Isolated strong to marginally severe storms could
occur further east into parts of Lower Michigan early Tuesday
morning.
...Upper Mississippi Valley/Great Lakes...
Today and tonight at mid-levels in the Mississippi Valley,
west-northwesterly flow will gradually transition to
west-southwesterly, as a subtle shortwave ridge moves eastward into
the Great Lakes. In response, low-level moisture advection will
strengthen over the central U.S., as a 50 to 60 knot 850 mb jet
develops across the central Plains. The northern edge of the
low-level jet will be located in the upper Mississippi Valley by
this evening. Strong lift associated with the jet will likely result
in convective initiation during the mid to late evening from
northeast Iowa into southern Wisconsin. RAP forecast soundings at
06Z in the La Crosse vicinity have MUCAPE increasing into the 2000
to 2500 J/kg range with effective shear forecast to be near 40
knots. In addition, 700-500 mb lapse rates are forecast to approach
8.5 C/km. This environment will likely support large hail with
elevated supercells that develop in the late evening and early
overnight period. Hailstones greater than 2 inches in diameter will
be possible.
Further east into Lower Michigan, convective initiation is expected
to occur by late in the period. Compared with areas to the west,
MUCAPE and lapse rates in Lower Michigan are forecast to be weaker.
For this reason, the hail threat there is expected to be more widely
spaced and marginal.
..Broyles/Squitieri.. 03/30/2026
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