ACUS01 KWNS 271211
SWODY1
SPC AC 271210

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0710 AM CDT Fri Jun 27 2025

Valid 271300Z - 281200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS LATE THIS
AFTERNOON INTO EARLY TONIGHT ACROSS THE NORTHERN PLAINS...AND THIS
AFTERNOON/EVENING ACROSS SOUTHEAST LOWER MICHIGAN...

...SUMMARY...
At least widely scattered thunderstorms are expected late this
afternoon/evening across the Dakotas and Nebraska, where very large
hail and severe outflow winds will be possible.  There will also be
a window of opportunity for tornadoes this evening across the
central Dakotas.  Occasional wind damage will be possible this
afternoon/evening across southeast Lower Michigan.

...Northern Plains late this afternoon into early tonight...
Water-vapor imagery this morning shows a mid-level disturbance
moving east across the northern Rockies.  This upper feature and an
associated belt of stronger flow will move eastward into the
northern Great Plains tonight.  In the low levels, southerly flow
will contribute to moisture return northward into the Dakotas as a
low develops near the SD/WY border.  Steep midlevel lapse rates of
8.5-9.5 C/km, and daytime heating will result in MLCAPE exceeding
4000 J/kg within the moisture plume where boundary-layer moisture is
highest.

A cap will likely inhibit storm development through the mid
afternoon before heating and the resultant erosion of convective
inhibition favors initially isolated storm development.  Forecast
soundings show very steep low to mid-tropospheric lapse rates, large
to extreme buoyancy, and effective shear supporting organized
storms.  The initial activity will likely be supercellular with an
attendant risk for large to giant hail with the stronger supercells.
A period of opportunity for an isolated tornado risk may realize
during the early evening, coincident with a slight intensification
of low-level shear, while maintaining a favorable storm mode. A
couple of clusters are forecast to evolve during the evening with
significant gusts (75-90 mph) possible in the more intense clusters.
A lingering risk for mainly wind and perhaps hail will gradually
wane towards the late evening and early overnight as this activity
gradually shifts east.

...Southeast Lower MI this afternoon/evening...
Not much change to the previous forecast scenario.  A midlevel
shortwave trough and associated weak wave cyclone now over the Upper
MS Valley will continue eastward over the Upper Great Lakes through
this evening, while a trailing cold front crosses Lower MI.  Daytime
heating and lower 70s deg F dewpoints will yield moderate buoyancy
by the early afternoon.  Low-level ascent along the front will
support a broken band of storms by mid afternoon, and the storms
will spread eastward before weakening by late evening.  Though
midlevel lapse rates and deep-layer vertical shear will not be
strong, ~35 kt midlevel flow and steep low-level lapse rates suggest
the potential for scattered 55-70 mph gusts capable of wind damage
with the stronger storms and linear clusters.

...Appalachians into the Southeast this afternoon/evening...
Another afternoon/evening of widely scattered thunderstorms and
isolated downburst potential is expected across a broad area from
the Appalachians into the Southeast/FL.  Local sea breeze
circulations, terrain circulations and residual outflow/differential
heating zones will help focus thunderstorm development. The more
intense storms and small-scale clusters will likely yield a risk for
45-65 mph gusts and pockets of wind damage.

..Smith/Broyles.. 06/27/2025

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