Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1254 AM CDT Sun Jun 28 2026
Valid 281200Z - 291200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE DAKOTAS
AND NORTHWEST MINNESOTA...AND ACROSS NORTHERN IOWA AND VICINITY...
...SUMMARY...
Severe thunderstorms are possible today across northern Iowa and
vicinity, and mainly tonight across the Dakotas. Large to very large
hail and severe winds are the primary hazards.
...Dakotas to IA/WI through tonight...
As the primary cyclone occludes near the southwest SK/southeast AB
border, a belt of south-southwesterly midlevel flow near 50 kt will
be maintained from CO to the Dakotas, east of the broad closed low
over the northern Great Basin/Rockies. A separate lee cyclone is
expected to form in the vicinity of northeast CO this afternoon and
then progress northeastward across NE/SD overnight. A storm cluster
will likely be ongoing near the southwest MN/northwest IA border at
the start of the period, as a continuation of the ongoing storms
along the NE/SD border. These morning storms will pose a threat for
occasional large hail/wind damage along the warm front/buoyancy
gradient through midday/early afternoon. In the wake of the morning
storms, a surface warm front demarcating boundary-layer dewpoints
into the 70s will likewise move northward slowly across IA into
southern MN/WI. West of the morning storms, a warm elevated mixed
layer observed in 00Z soundings across the central Plains will act
to cap the moistening boundary layer and likely inhibit additional
warm sector storm development through much of the period. A few
storms will be possible in ND during the afternoon, though storm
coverage/intensity are both in question given weak-moderate buoyancy
and limited forcing for ascent.
Much of the severe threat will likely be delayed until tonight
immediately north of the lee cyclone into SD. Westward advection of
richer moisture and ascent preceding the surface cyclone (and subtle
embedded speed maxima aloft) will likely support elevated
thunderstorm development overnight across western SD into southern
ND. The environment will favor elevated supercells capable of
producing very large hail (2-3 inches in diameter) and occasional
severe gusts.
Farther east, a zone of low-level warm advection will be focused
across WI by late evening/early tonight along the northeast edge of
the warm elevated mixed layer. Sufficient moistening above the
surface and large CAPE will favor the potential for at least
isolated large hail/strong gusts with largely elevated storms
tonight.
...Carolinas/southern VA this afternoon/evening...
An MCV now over KY will turn more southeastward today, downstream
from an amplifying ridge over the lower and middle MS Valley.
Destabilization and steepening of low-level lapse rates in cloud
breaks, along with ~25 kt midlevel flow, will support isolated wind
damage potential with storm clusters during the afternoon/evening.
...West TX late this afternoon/evening...
Strong surface heating and deep mixing along a sharpening dryline
will allow high-based thunderstorm development from late afternoon
through late evening. Flow aloft will be weak, but inverted-V
profiles will favor isolated severe outflow gusts of 60-75 mph.
..Thompson/Chalmers.. 06/28/2026
Read more CHECK UPDATE ZOOM GRAPHIC
http://dlvr.it/TTFfxr
