ACUS01 KWNS 111300
SWODY1
SPC AC 111258

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0758 AM CDT Thu Jun 11 2026

Valid 111300Z - 121200Z

...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS ACROSS EASTERN
IOWA AND NORTHERN ILLINOIS...

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE NORTHEAST/MID-ATLANTIC STATES...

...SUMMARY...
Widespread severe thunderstorms are expected across parts of the
Midwest and Great Lakes region, including Iowa, northern Missouri,
northern Illinois and southern Wisconsin to Lower Michigan and
northern Indiana. This includes the potential for widespread/intense
damaging winds, large hail, and tornadoes, some of which may be strong.

...Midwest/Great Lakes...

Portions of the region have been upgraded to a Moderate Risk.
Another very active day with widespread/intense severe storms is
expected regionally. A consequential severe risk is already ongoing
this morning across Iowa/far northern Missouri, and will continue
east-northeastward and become more prominent regionally during the
day. A well-organized/eastward-accelerating bowing cluster of
storms, now supported by an apparent MCV, has had a history of
measured severe-caliber wind gusts overnight and in the predawn
hours from southeast Nebraska into southern Iowa. A similar severe
risk should continue east-northeastward through midday across
eastern Iowa/far northeast Missouri toward northern Illinois, with
more of a surface-based/tornado risk potentially unfolding
relatively early today aside from a continued prominent damaging wind threat.

Scenario is supported by a robust southwesterly low-level
jet/moisture transport, even with some diurnal weakening of the
low-level jet possible. Also influential is a prominent/increasingly
neutral-tilt-shortwave trough and jet streak crossing the Corn Belt,
notably strong features by mid-June standards.

Convective overturning/outflow from last evening's MCS are still
residual factors evident this morning in observational
data/supplemental 3D mesoanalysis across far eastern Iowa, far
northeast Missouri into central Illinois. This is sampled by the 12z
observed sounding from KILX/Lincoln, IL. These residual factors may
somewhat southward-focus the peak/most-intense severe weather later
today, with more uncertainty progressively northward in general
proximity to Lake Michigan latitudinally, including parts of
Wisconsin/Michigan. The timing/residual impacts of this morning's
MCS across Iowa/northern Missouri into northern Illinois and severe
potential in its wake near the surface low and front, and/or to its
(MCS) north-northeast are a bit less uncertain. That said, mass
response/fluxes related to the dynamic shortwave trough/speed max
will be notable and consistent with heightened severe-potential even
if outflow/cloud debris exists and sub-regional areas of
destabilization are sub-optimal.

Details of later-afternoon severe potential is somewhat contingent
on how the morning MCS further evolves, but a window for
redevelopment in its immediate wake will probably exist. This will
lead to a renewed round of severe storms as development occurs near
the cold front, and perhaps preferentially favors prior outflow,
with a damaging wind and tornado risk continuing eastward this
evening as the low-level jet re=intensifies and as storms gradually
grow upscale toward Lake Michigan and across Illinois/Indiana/Lower Michigan.

...Eastern Kansas and Southern Plains...

Additional thunderstorm development is expected along the trailing
cold front into portions of the central/southern Plains. Deep layer
shear will be maximized in the post-frontal environment; however,
around 20-30 kt of effective bulk shear and moderate to strong
instability will support some supercell structures capable of large
hail and damaging winds. Storm motions and boundary parallel shear
will likely lead to clustering and messy modes over time.

...Mid-Atlantic ad central Appalachians...
Forcing for ascent from multiple shortwave disturbances across the
northeast and dewpoints in the 60s to 70s F will support development
of widely scattered thunderstorms by afternoon across the
Mid-Atlantic into the central Appalachians. Though vertical shear
will be generally weak, moderate to strong instability will be in
place will support stronger updrafts capable of damaging winds. It
is likely that several clusters will emerge with potential for
organizing along cold pools and more focused corridors of damaging
wind potential.

..Guyer/Wendt.. 06/11/2026

$$
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