830
ACUS48 KWNS 230728
SWOD48
SPC AC 230726

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0226 AM CDT Thu Jul 23 2026

Valid 261200Z - 311200Z

...DISCUSSION...
...Days 4-5/Sun-Mon -- Upper Midwest toward the Ohio Valley...

Enhanced northwesterly flow aloft will overspread the Upper Midwest
to the Ohio Valley on Sunday and Monday as several shortwave
impulses migrate through the area on the eastern periphery of a
strong upper ridge over the Plains. A seasonally very moist airmass
will reside across much of these areas, supporting strong
destabilization each day. On Sunday, a corridor of severe
thunderstorm potential appears possible across parts of MN/WI toward
northern IA/IL as a weak shortwave impulse initially over the
Dakotas spreads east. While details regarding storm coverage remain
uncertain, sufficient deep layer shear and strong instability will
be in place, and at least isolated storm clusters could pose a risk
for damaging winds.

By Monday, an upper shortwave trough will emanating from an upper
low near Hudson Bay will dig southward across the Great Lakes. This
will result in increasing northwesterly flow aloft. Meanwhile, a
surface low may move eastward across the Great Lakes near the
international border while a stronger nocturnal low-level jet
develops over parts of the Great Lakes and Ohio Valley. This
stronger flow will overspread a moist and unstable airmass, and
potential for thunderstorm clusters developing into an MCS appears
possible.

While details remain uncertain regarding convective evolution and
coverage on Sunday and Monday, through broader synoptic pattern
appears favorable for at least isolated severe thunderstorms. The 15
percent severe areas may shift some in the coming days as details
become more clear.

...Days 6-8/Tue-Thu...

It is possible some severe potential could shift east/southeast on
Tuesday toward the central Appalachians and the Mid-Atlantic.
Deep-layer northwesterly flow will not be as strong as prior days,
but could still be sufficient for some organized severe risk.
Confidence in where greater risk corridors may develop is low, and
will largely be influenced by convective evolution in the Days
4-5/Sunday-Monday periods.

A strong upper ridge will shift west across the western U.S. late in
the period, bringing a broad area of generally weak deep-layer
northwesterly flow to the eastern half of the CONUS. Some
thunderstorm potential is likely within this typical summertime
pattern across the Plain into the East, but severe potential is
uncertain.

..Leitman.. 07/23/2026