651
ACUS01 KWNS 270104
SWODY1
SPC AC 270102

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0802 PM CDT Sun Jul 26 2026

Valid 270100Z - 271200Z

...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS PORTIONS OF THE
UPPER MIDWEST AND WESTERN GREAT LAKES...

...SUMMARY...
Severe thunderstorms capable of large to very large hail, damaging
winds (possibly 75+ mph), and tornado risk remain likely from the
upper Mississippi Valley and Great Lakes southwestward into
Nebraska, mainly late this evening and tonight.

...Upper Midwest...
A very unstable environment remains in place across the region, with
the MPX, GRB, and DVN 00Z soundings sampling MLCAPE from 3100, 2900,
and 2800 J/kg, respectively. Surface observations show mid to upper
70s dewpoints on the warm side of the warm front extending from
north-central MN through northeast WI/far western Upper MI. A
thunderstorm has matured upstream of this corridor, with the
expectation it will remain strong to severe as it continues
southeastward. Modest low-level warm advection into this boundary
will also contribute to additional thunderstorms this evening and
overnight. Environmental conditions are still expected to support
large to very large hail early in the convective cycle while a more
cellular mode is likely. Thereafter, a trend towards bowing segments
capable of severe wind gusts is anticipated. A singular MCS could
eventually develop, with severe gusts possible as it moves southward
as well. Some gusts, both within the line segments and early in the
MCS lifecycle, could be significant (i.e. over 75 mph).

...TN Valley...
A cold-pool-driven MCS continues to propagate south-southeast at
approximately 40 kts. The downstream airmass is very moist, with
numerous sites reporting dewpoints in the low 80s. This moisture is
contributing to extreme buoyancy, with the recent 00Z BNA sounding
sampling 4500 J/kg of SBCAPE. This MCS is also oriented
perpendicular to the deep-layer vertical shear. All of these factors
will contribute to continued southward progression, with an
attendant risk for strong gusts likely extending into Middle TN this
evening.

...South-Central into Southeast SD into central NE...
Numerous attempts at deep convection along the weak surface trough
extending from south-central SD through central NE have failed thus
far. The window of opportunity for deep convection will likely
remain open for the next hour or two before building inhibition
associated with nocturnal cooling precludes mature convection. Until
that occurs, there remains a conditional risk for severe
thunderstorms capable of strong downdrafts and isolated large hail.

...Elsewhere...
Increasing thunderstorm coverage is possible across the Mid-Atlantic
over the next few hours as a shortwave trough progresses
southeastward across the region. Moderate vertical shear could
support updraft organization with deeper, more persistent
convection. Isolated damaging gusts and hail are possible with the
more organized storms. Isolated damaging gusts remain possible
across northern Wyoming and far southwest South Dakota as high-based
thunderstorms track northeastward across the region this evening.
Jackson Hole Wyoming reported a gust of 50 kt at 2353Z.

..Mosier.. 07/27/2026

$$