Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0755 PM CDT Sun Jun 28 2026
Valid 290100Z - 291200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF
THE NORTHERN PLAINS...
...SUMMARY...
Severe thunderstorms are possible tonight across the Dakotas. Large
to very large hail and severe winds are the primary hazards. More
isolated severe storms capable of large will be possible in northern
Wisconsin late tonight into early tomorrow morning.
...Discussion...
Water vapor imagery this evening shows a mid-level trough located
across northern Montana into Alberta/Saskatchewan. At the surface, a
low is occluding to the north across southern Alberta, with a
secondary low developing across eastern Colorado. A surface cold
front extends across portions of the western Dakotas north to the
occluding front in Canada. As the surface low in Colorado deepens
and moves northeastward late this evening, thunderstorm activity is
expected to increase in coverage near the low/cold front and along a
warm front lifting into the Upper Midwest.
...Northern Plains...
Initial thunderstorm development has occurred this evening within a
zone of weak low-level convergence in central/western North Dakota
as enhanced mid-level westerly flow overspreads the region from the
trough to the west. Daytime heating and dew points in the upper 60s
F have led to strong buoyancy across the region. Low-level flow is
rather weak but deep layer shear around 50-55 kts will likely
support a few isolated supercells capable of large to very large
hail. See MCD#1369 for more information.
Additional thunderstorm activity is progged to develop overnight as
the surface low moves northward and forcing for ascent continues to
increase. Aforementioned strong instability and deep layer shear
profiles will support supercells capable of large to very large
hail. The Slight Risk was maintained with this update to account for
this potential overnight. See MCD#1370 for more information.
...Upper Midwest...
Thunderstorm development is expected along and north of a warm front
lifting into northern Wisconsin late tonight into early Monday
morning. As the warm front lifts northward, moisture and instability
will increase from the south. Moderate to strong instability
overlapping increasing deep layer shear from the trough to the west
will support a mix of supercells and multi-cell clusters with
potential for large hail. A Marginal Risk was maintained across
central/northern Wisconsin and extended into the northern Lower
Michigan Peninsula to account for this potential.
...West Texas...
A few stronger storms may continue across portions of western Texas
near dryline and south to the Trans Pecos with a few instances of
marginally severe hail and gusty winds. Loss of daytime heating
should limit the duration of this risk past sunset with storms
decreasing in coverage and intensity.
..Thornton.. 06/29/2026
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