Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0258 PM CDT Mon Mar 30 2026
Valid 302000Z - 311200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM CENTRAL IOWA
INTO SOUTHERN WISCONSIN...NORTHERN ILLINOIS...AND LAKE MICHIGAN...
...SUMMARY...
A few severe thunderstorms with large hail, are expected across
parts of the middle and upper Mississippi River Valley tonight
through early Tuesday morning. Isolated strong to marginally severe
storms could occur farther east into parts of Lower Michigan early
Tuesday morning, and over the Texas South Plains this afternoon and
evening.
Little change was made to the outlook at 20Z. Storms are still
expected to form near or after 00Z over IA as a weak midlevel wave
moves out of NE, and theta-e advection around 850 mb increases on
the nose of the nocturnal low-level jet. Hail and locally strong
gusts will be possible.
As the increasing moisture spreads farther north overnight, it will
interact with the east-west oriented frontal zone from southern WI
into Lower MI, with additional development expected. Areas of hail
remain possible as lapse rates aloft will be steep. Moderate
deep-layer mean wind speeds should also result in corridors of
strong to damaging gusts as storms amass outflow.
Uncertainty remains regarding coverage of storms overnight.
Conditionally, strong westerly mean wind speeds and presence of dry
air in the low-levels may favor damaging wind gusts, perhaps
crossing Lake MI and into Lower MI overnight should a substantial
cluster of storms remain intact.
..Jewell.. 03/30/2026
.PREV DISCUSSION... /ISSUED 1113 AM CDT Mon Mar 30 2026/
...IA to Lower MI...
Fast zonal flow is present across the northern tier of states today,
with minor perturbations embedded within the flow field affecting
the upper MS Valley and Great Lakes region. A combination of
daytime heating, low-level warm/moist advection, and increasing
low-level convergence along a surface baroclinic zone will result in
scattered thunderstorms after dark over IA. These storms will form
in an environment of steep mid-level lapse rates and strong
deep-layer shear. MLCAPE values around 1500 J/kg will promote
strong updrafts with a few supercells possible. Large hail appears
to be the main threat with these storms as they progress eastward
into northern IL/southern WI and slowly weaken with diurnal cooling.
Storms will persist through the night and spread across much of
lower MI. Despite weak instability, a few CAM solutions maintain
vigorous updrafts, supporting a low risk of hail and gusty winds
overnight.
...TX Panhandle...
Full sunshine and dewpoints in the 50s will yield a moderately
unstable air mass along the dryline over the TX Panhandle this
evening. Most CAM guidance show isolated thunderstorm development
in this region - mainly in the 23-03z period. Forecast soundings
suggest the low/mid troposphere is dry and will limit the number of
updrafts that can survive. However, any storm that can persist will
pose a risk of gusty winds or hail.
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