Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0258 PM CDT Mon Jul 27 2026
Valid 272000Z - 281200Z
...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS OVER PARTS OF
THE LOWER GREAT LAKES AND MIDWEST STATES...
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PARTS OF THE
CENTRAL AND NORTHERN HIGH PLAINS....
...SUMMARY...
Severe storms capable of strong to severe wind gusts and large hail
are expected across the Great Lakes and Midwest through tonight.
More sporadic occurrences of damaging wind are possible in the
Mid-Atlantic, Tennessee Valley, central High Plains, and southeast
Arizona.
...20z Update IL/IN...
An evolving convective cluster across northern IL/IN and southern
lower MI should continue to move south/southeast this afternoon.
Low-level convergence is maximized along a weak CAPE/ThetaE gradient
laying roughly near the IN/OH border. CAM guidance and observation
trends suggest this may provide a focus for convection through this
afternoon and evening gradually turning the cluster further
southward. Moderate buoyancy and 40+ kt of deep-layer shear parallel
to the boundary could support organized linear/bowing structures
with severe/damaging gusts and perhaps some QLCS tornadoes possible
across northern IN and possibly extending into western OH. However,
leading stratiform and cloud cover could limit the eastern extent of
the higher severe risk, and confidence in the convective evolution
is very low.
Additional development has been noted along the western flank of the
complex over northern IL, with another cluster of storms exiting
southern WI. It is possible that these new storms, and additional
ascent tied to a westerly low-level jet will support a second
cluster of severe storms eventually organizing and moving more south
across IL/IN. Hot surface temperatures (90-95 F) and a very large
reservoir of extreme buoyancy (MUCAPE 4000-5000 J/kg) extending into
IL and western IN would support a risk for widespread
severe/damaging gusts. Given the increased confidence in damaging
winds this afternoon/evening, have shifted 30% wind probabilities
farther south in IN.
...Central and northern High Plains...
Scattered storms ongoing over the high plains should increase in
coverage and intensity this afternoon. Steep mid-level lapse rates
could promote severe wind gusts with stronger downdrafts, along with
isolated hail. Minimal changes were made to the prior outlook, see
MCD#1767 and MCD#1768 for more information.
Additional scattered thunderstorms are ongoing over parts of the Mid
Atlantic/Southeast and southern AZ. These storms should continue
this afternoon with potential for sporadic damaging gusts owing to
heavy water loading and moderate buoyancy. Limited vertical shear
and only modest clustering suggest severe potential will remain
isolated before diminishing overnight.
..Lyons.. 07/27/2026
.PREV DISCUSSION... /ISSUED 1149 AM CDT Mon Jul 27 2026/
...Midwest/Ohio Valley...
A large upper ridge remains present today over the central
Plains/Rockies, with moderately strong northwest flow aloft from the
Midwest into the OH Valley. A very moist and unstable low-level air
mass resides from WI/IL into MI/IN/OH, where mostly clear skies will
result in hot afternoon temperatures and MLCAPE values over 3000
J/kg. Multiple clusters of intense thunderstorms are ongoing over
parts of WI tracking southeastward. These storms will move through
this reservoir of high CAPE, leading to the potential for an active
severe weather event today. However, details of how these clusters
evolve are uncertain.
Vertical shear across this region will support supercell structures,
capable of damaging winds, hail, and isolated tornadoes this
afternoon. However, the greater concern is if storms can congeal
into a southeastward bowing system and that sweeps across Lower MI,
eastern IL, IN, and western OH. Several morning CAM solutions
indicate that risk, with storms spreading into KY overnight before
weakening. Unfortunately, this synoptic pattern does not lend
itself to a high-confidence convective forecast.
...High Plains...
Widespread clouds are affecting parts of western NE this morning.
However, strong heating will occur north and south of these clouds,
leading to afternoon thunderstorms. The most active area will
likely be over the Black Hills region where damaging winds and hail
are possible. Farther south, widely scattered high-based
thunderstorms will affect eastern CO/western KS with a risk of
damaging wind gusts.
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