762
ACUS01 KWNS 280542
SWODY1
SPC AC 280541

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1241 AM CDT Sat Jun 28 2025

Valid 281200Z - 291200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM THE UPPER
MIDWEST TO THE BLACK HILLS REGION...

...SUMMARY...
Scattered strong to severe thunderstorms, perhaps including one or
two organizing clusters, will pose a risk for severe hail, wind and
perhaps a couple of tornadoes across parts of the Upper Midwest into
the Plains of South Dakota and Nebraska.

...Upper Midwest to the Black Hills of South Dakota...

Seasonally typical early summer pattern will be noted today as
stronger westerlies are confined to the northern U.S., and much
weaker flow is observed across the southern two-thirds of the CONUS.
Latest water-vapor imagery suggests a few weak disturbances are
translating across the northern Rockies toward the northern Plains
and this will shunt the primary synoptic boundary across much of the
Dakotas into the upper MS Valley by early evening. This boundary
will prove instrumental in focusing deep convection during the
afternoon/evening hours.

Early this morning, scattered clusters of strong/severe
thunderstorms are propagating southeast across the eastern Dakotas.
This activity will advance into the upper MS Valley early in the
period as LLJ focuses across eastern SD into northern MN. While some
severe threat will be noted with a possible MCS at daybreak,
convective outflow will largely influence subsequent regeneration.
Latest model guidance suggests an east-west boundary will drape
itself across western WI/southern MN by 18z, likely modified by the
aforementioned early-day MCS. Boundary-layer heating is expected to
aid buoyancy across the Dakotas southeast of the cold front, and
scattered thunderstorms should readily develop along this wind shift
by late afternoon, aided in part by a weak short wave trough.
Additional convection is also possible along the outflow. Wind
profiles favor some supercell development, along with possible
clusters. Very large hail could accompany supercells. The east-west
boundary should enhance low-level shear such that a higher
probability for tornadoes will exist across southern portions of MN.

Stronger heating across the Plains of NE into eastern WY will aid
isolated-scattered thunderstorms across this portion of the SLGT
Risk. Higher-based updrafts, but steep lapse rates suggest hail/wind
will be the primary concerns.

...Northern Middle Atlantic region and upper Ohio Valley...

Weak short-wave trough is advancing east across the upper Great
Lakes region early this morning. Southern influence of this feature
will encourage convective development by 18z across the upper OH
Valley into upstate NY. Modest west-southwesterly flow at mid levels
suggests some convective organization is possible; however, poor
lapse rates and modest instability should result in mainly a
damaging wind threat with the most organized convection. Some
consideration was given for higher probabilities across portions of
the northern Middle Atlantic into southern NY, but weak lapse rates
are concerning and deep-layer shear is not that strong. Even so,
gusty winds will likely be noted with this activity as it spreads
across PA/NY toward the western parts of southern New England.

..Darrow/Lyons.. 06/28/2025

$$