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Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
1136 AM CDT Wed Aug 28 2024

Valid 281630Z - 291200Z

...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
NORTH DAKOTA/SOUTH DAKOTA...

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE
MIDWEST/OHIO VALLEY TO MID-ATLANTIC...

...SUMMARY...
Severe thunderstorms are expected across parts of the Dakotas and
from the Ohio Valley to the Mid-Atlantic Coast.

...Dakotas...
Have upgraded portions of south-central North Dakota/north-central
South Dakota to a categorical Enhanced Risk for what should be a
relatively greater likelihood and concentration of severe storms
late this afternoon through early/mid-evening.

A prominent upper-level trough centered over western Montana and
southern Alberta will continue generally eastward over the Canadian
Prairies and toward the northern High Plains, with a
trough-preceding/basal upper-level jet resulting in considerably
strengthening southwesterly winds aloft by peak heating into
tonight. This will be atop an increasingly moist boundary layer
(dewpoints increasing through the 60s F) ahead of a surface low
across South Dakota and a front extending northward into North
Dakota.

Thunderstorms should develop near the front by late afternoon/early
evening, perhaps initially across North Dakota where overall forcing
will be greater, and subsequently southward into South Dakota where
richer low-level moisture and greater buoyancy will reside. Given
steep lapse rates and the reservoir of instability, these initial
storms should be supercells capable of very large hail amidst
strengthening flow aloft. Large to very large hail and severe wind
gusts will be the most co*mon hazards, although a tornado risk may
also exist particularly across north-central South Dakota/far
south-central North Dakota near the surface low/warm front-related
triple point where moisture/low-level SRH will be maximized. Over
time, relatively weak mid-level flow may encourage a transition to
messier, quasi-linear modes with embedded LEWP/bow formations for a
few hours. Activity should weaken overnight as it moves into
stabilizing boundary-layer air, though a 45-55-kt low-level jet may
encourage persistence of a cluster or two tonight into the eastern
Dakotas.

...Midwest/Ohio Valley to Mid-Atlantic States...
Widely scattered to scattered thunderstorms will pose a risk for
damaging winds particularly mid/late afternoon through
early/mid-evening regionally. Some hail may also occur on a more
marginal and isolated basis. This severe risk will primarily span
parts of Indiana/Ohio eastward to the coastal Mid-Atlantic/Delmarva
vicinity, although the overall extent and magnitude of today's risk
is still a bit uncertain.

The boundary layer will not be overly moist by late-summer
standards, particularly across the middle Ohio River Valley, but a
relatively richer moist axis (through the lowest 2-3 km AGL) extends
this morning from the upper Ohio Valley eastward toward the coastal
Mid-Atlantic/Northeast. The boundary layer will also not be overly
unstable later today, with severe-adequate MLCAPE generally limited
to 2000 J/kg MLCAPE. 

Aside from differential heating related to last night's convection
across the Midwest, several impetuses for thunderstorm development
to the south of the primary Great Lakes front may include the
eastward transitions of MCVs across southeast Lower Michigan and
north-central Illinois, which should be influential into the Lake
Ontario/New York/northern Pennsylvania and lower/middle Ohio Valley
vicinities, respectively, later this afternoon and evening.
Effective shear will tend to be limited to 20-25 kt, but
slowly-increasing-with-height deep-layer westerlies will support
multicell-related damaging wind/some hail potential as low-level
lapse rates steepen and the boundary layer moderately destabilizes
this afternoon.

..Guyer/Wendt.. 08/28/2024