739
ACUS02 KWNS 231732
SWODY2
SPC AC 231730

Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1230 PM CDT Sun Jun 23 2024

Valid 241200Z - 251200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS IN PARTS OF THE
UPPER MIDWEST...

...SUMMARY...
Scattered severe thunderstorms will be possible over parts of the
Upper Midwest, mainly from late afternoon Monday into Monday night.
A low-probability scenario of a severe MCS producing destructive
wind gusts is apparent, centered on central parts of Minnesota into
Wisconsin.

...Upper Midwest...
Confidence in tomorrow`s severe evolution is low. A wide range in
potential outcomes from a sporadic primarily elevated large hail
threat to a derecho scenario are plausible. Primary change with this
outlook is to add a significant severe wind area for the conditional
potential of destructive wind gusts from an intense MCS.

A shortwave trough should amplify somewhat over the southern Prairie
Provinces, mainly during the latter portion of the period. This will
induce weak mid-level height falls by Monday evening/night across
northern portions of the Upper Midwest. Primary surface cyclone will
similarly track east from southeast SK to far northwest ON. A
north/south-oriented cold front attendant to this cyclone should
push east across the northern Great Plains, with the trailing
portion slowing and eventually stalling near the SD/NE border area.

A very stout EML characterized by 700-mb temperatures of 14-16 C
will inhibit surface-based warm sector development through much of
the day, with remnant elevated convection from late D1 over ND
potentially persisting on an isolated basis along the periphery of
the EML, mainly over northern MN. Large to extreme buoyancy will
develop, centered on eastern SD into western MN, with MLCAPE in
excess of 4000 J/kg probable.

Isolated late-afternoon to early-evening storm development will be
possible near the cold front over eastern ND into
west-central/northwest MN. Guidance differs greatly on whether this
will occur or not given the stout capping to the southeast. A more
probable scenario is for elevated convection to develop during the
evening into the overnight as a low-level jet intensifies from the
Mid-MO Valley towards Lake Superior. Guidance also differs on the
evolution of the surface warm front into Monday evening/night with
the 12Z NAM holding farther south and more pronounced with the
baroclinic zone across central MN. Most other guidance advances the
warm front deeper into northern MN. Given these spatial concerns
along with the relatively weak forcing for ascent near/just after
peak heating amid pronounced capping over the open warm sector,
confidence is low in the most likely scenario of convective
evolution. Isolated, very large hail will be possible given
plentiful elevated MUCAPE and strengthening effective bulk shear.
The 12Z HRW-ARW depicts a more ominous scenario with surface-based
development over the Upper Red River Valley growing upscale into an
intense, bowing MCS through central portions of MN/WI. This includes
a signal for extreme rear-inflow jet development to around 95 kts at
the mature stage over west-central WI. Other guidance suggests a
later MCS may develop out of the elevated convection in north parts
of MN/WI, and still other guidance suggests little, if any MCS
development will occur. The decision has been made to defer on a
categorical upgrade and await potentially more consistent guidance
in later outlook cycles.

...Black Hills vicinity into parts of NE and western IA...
The southern portion of the weak cold front should slow and stall
near the SD/NE border area by early evening Monday. Strong heating
in the vicinity of the boundary will support isolated to widely
scattered high-based thunderstorm development. With generally weak
mid-level flow across the region, storms may quickly become outflow
dominant, but steep tropospheric lapse rates will support at least
isolated severe gusts. The strongest updrafts may also be capable of
producing some hail.

...Coastal Carolinas...
A cold front is forecast to move across the coastal Carolinas
vicinity, with scattered thunderstorm development expected during
the afternoon. Moderate to locally strong prefrontal buoyancy (with
MLCAPE of near/above 2000 J/kg) and effective shear generally around
25-30 kt will support potential for a few stronger multicells and
perhaps a marginal supercell or two, with an attendant threat of
locally damaging winds and hail.

..Grams.. 06/23/2024

$$