ACUS01 KWNS 111954
SWODY1
SPC AC 111953

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0253 PM CDT Thu Jun 11 2026

Valid 112000Z - 121200Z

...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS
OF THE MIDWEST...

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE UPPER
OHIO VALLEY AND MID-ATLANTIC REGIONS...

...SUMMARY...
Widespread severe thunderstorms are expected this afternoon and
evening across parts of the Midwest and Great Lakes region,
including far eastern Iowa, northern Missouri, northern/central
Illinois, southern Wisconsin, Lower Michigan, and northern Indiana.
This includes the potential for widespread/intense damaging winds
(some 75+ mph), large hail, and several tornadoes, some of which may
be strong to intense.

...20z Update...
The previous forecast remains mostly on track with only minor
adjustments made. Across the Midwest, latest GOES imagery shows
gradual clearing across southern IA/northern MO/western IL behind a
decaying MCS. Surface observations across southern IA show some
degree of air mass recovery is ongoing; however, the quality of
destabilization with northeastward extent remains very uncertain
given more extensive cloud cover, additional precipitation, and the
rapid approach of the cold front from the west.

Nonetheless, regional 18z RAOBs and VWPs are sampling the approach
of a 60-70 knot mid-level jet, which heralds the onset of stronger
synoptic ascent across the upper MS Valley. Southerly low-level flow
should strengthen through the evening in response to increasing
ascent, which will likely help advect higher theta-e air
north/northeastward as well as begin to augment low-level SRH.
Recent MRMS composites show the onset of convective initiation along
the cold front, which should maintain sufficient residence time
within the returning theta-e plume for further strengthening over
the coming hours. Latest high-res ensemble guidance (including WoFS
and time-lagged HRRR/RRFS solutions) appear to be capturing these
trends well and continue to depict the corridor of highest severe
wind and tornado threat across the Moderate risk zone. As such,
little change was made to the ongoing probability and intensity contours.

...Upper OH Valley/Mid-Atlantic...

Several loosely organized convective bands have emerged across
eastern OH into western PA/NY. Regional VWPs continue to sample
deep-layer bulk shear on the order of 15-20 knots, which casts doubt
on the eastward extent of the severe wind threat beyond 00-02 UTC
when nocturnal stabilization will begin to weaken convection. Recent
CAM guidance suggests the peak wind threat should remain across
western to central PA/NY, which casts considerable uncertainty on
severe wind coverage further east along the Mid-Atlantic coast.
Consequently, the 30% wind probabilities have been shifted west to
better align with recent observed and modeled trends. (See MCDs
#1091 and #1092 for additional details.)

...Southern Plains...

Recent surface observations show the cold front rapidly pushing
southeast across TX, OK, and southeast KS. Building cumulus is also
noted along the front, which suggests convective initiation is
probable in the coming hours. These trends align with the previous
forecast, see MCD #1090 for additional short-term details.

..Moore.. 06/11/2026

.PREV DISCUSSION... /ISSUED 1122 AM CDT Thu Jun 11 2026/

...Midwest/Great Lakes...

An active and impactful severe weather event is still expected
across parts of the Midwest Great Lakes later this afternoon and
evening. Ongoing bowing cluster across southeast IA/northwest
IL/southwest WI and vicinity may continue to pose at least some
severe wind and embedded QLCS tornado threat as it continues
east-northeastward across parts of the Midwest this afternoon. There
is still airmass recovery underway ahead of this activity,
especially into central/northern IL, northern IN, and parts of
southern Lower MI where strong heating is occurring. Enhanced
mid-level west-southwesterly winds associated with a potent
shortwave trough over the northern Plains/Upper Midwest will
overspread the developing warm sector this afternoon, and support
organized severe potential, including the possibility of multiple
tornadic supercells and widespread severe/damaging winds.

Even so, greater than usual uncertainty exists regarding
redevelopment later today on the southern/western flank of ongoing
convection across northern IL into northeast MO and vicinity. A
gradual increase in both low-level and deep-layer shear is
anticipated across this area as a 30-40+ kt southerly low-level jet
develops eastward in tandem with the eastward-ejecting shortwave
trough and mid-level jet. A mix of supercells and bowing segments
appears probable as renewed thunderstorms develop along/ahead of the
surface cold front this afternoon in a strongly unstable and rather
favorably sheared environment. If at least semi-discrete supercell
structures can be maintained, then potential exists for several
tornadoes, and multiple strong to intense tornadoes (EF-2/3+) given
the enhanced low-level shear. Isolated large to very large hail may
also occur with any sustained supercells.

Otherwise, numerous to potentially widespread severe/damaging winds
also appear likely through the period across parts of
northern/central IL into southern Lower MI and northern IN. Both the
ongoing cluster and eventual upscale growth of convection that
develops this afternoon will likely produce severe/damaging winds,
some of which could be significant (75+ mph). The northern extent of
the severe risk into WI and northern Lower MI remains uncertain, but
at least some wind and/or tornado threat will likely continue with
eastward extent into the southern Great Lakes and northern IN this evening.

...Eastern Kansas/Southern Missouri into the Southern Plains...

Additional thunderstorms will likely develop this afternoon and
evening along the trailing cold front into portions of eastern
KS/southern MO into the southern Plains. Stronger deep-layer shear
is forecast to lag behind/to the north of the cold front. Still,
around 20-30 kt of effective bulk shear and moderate to strong
instability will support marginal supercell structures and loosely
organized multicells capable of producing both large hail and
damaging winds. A large component of boundary-parallel shear will
likely lead to clustering and messy convective modes through the
evening before thunderstorms gradually weaken with the loss of
daytime heating.

...Mid-Atlantic/Central Appalachians...

Recent visible satellite imagery across much of the Mid-Atlantic and
central Appalachians shows mostly sunny to partly cloudy conditions,
with ample low-level moisture present per latest surface
observations and area 12Z observed soundings. Large-scale ascent
associated with multiple low-amplitude mid-level shortwave troughs
will likely support the development of widely scattered
thunderstorms by afternoon across parts of the Mid-Atlantic into the
central Appalachians. Though deep-layer shear is forecast to remain
modest, moderate to strong instability will exist with continued
diurnal heating this afternoon. This will support stronger updrafts
capable of scattered severe/damaging winds and perhaps isolated
hail. Multiple clusters should eventually emerge, with potential for
organizing along outflow/cold pools, and more focused corridors of
damaging winds possible across parts of the I-95 corridor from
northern VA to eastern PA and NJ.

$$
--- SBBSecho 3.28-Linux
 * Origin: Capitol City Online (618:250/10)