118
ACUS01 KWNS 240554
SWODY1
SPC AC 240552

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1252 AM CDT Fri May 24 2024

Valid 241200Z - 251200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS IN PARTS OF THE
MIDWEST TO THE MID-SOUTH AND SOUTHERN GREAT PLAINS...

...SUMMARY...
Scattered severe thunderstorms will be possible from parts of the
Midwest to the Mid-South and southern Great Plains, mainly this
afternoon and evening. Greatest potential for a few tornadoes exists
across central to northern Illinois, far eastern Iowa, and southern
Wisconsin.

...Upper MS Valley to the Mid-South and southern Great Plains...
An MCS will be ongoing at 12Z, likely approaching the Upper MS
Valley. 00Z CAM guidance runs the gamut on the evolution of this MCS
through late morning into midday. Some suggest it will weaken as it
outpaces the instability axis lagging to its southwest over the
Lower MO Valley to the southern Great Plains. Others indicate that
the southern flank of the MCS may intensify across the Mid-MS Valley
into IL, as diurnal destabilization ensues along the instability
gradient. Thus, large-scale outflow boundary placement varies
considerably by afternoon from far southern WI to far southern MO.

The surface cyclone over southeast ND will curl north-northeast into
southeast MB and occlude, as it becomes vertically stacked beneath
its attendant mid-level low. Daytime mid-level height falls,
coincident with stronger low-level shear, will be most pronounced
over the Upper MS Valley. These will be weaker with southward extent
over the Mid-MS Valley. A predominately zonal mid-level flow regime
is expected farther south with minimal height change. However,
low-level convergence should be adequate for isolated to scattered
thunderstorm development along the trailing cold front from the
Upper MS Valley to eastern OK and the dryline into central TX.

While the more favorable low-level shear and ascent will be focused
north, aforementioned uncertainties over the degree of
destabilization related to the evolution of the morning MCS preclude
a greater categorical risk. Conditionally, the remnant outflow
boundary will likely provide a focus for greater supercell tornado
potential. Primary change this outlook is to expand both the 2
percent tornado probability north in WI and the 5 percent prob south
in IL.

Very large buoyancy is expected from the Ozark Plateau southward
with MLCAPE of 3500-4500 J/kg. Despite the lack of appreciable
large-scale ascent beyond the front/dryline, this degree of
instability, coupled with pronounced mid to upper-level speed shear,
should favor potential for very large hail with initial supercell
development. Given the frontal forcing, a few clusters may evolve
downstream during the evening across parts of the Mid-South to
central TX with a mixed large-hail and damaging-wind threat.

...GA to the Carolinas...
A parade of MCVs moving eastward across the southern states will aid
in isolated-scattered afternoon to early evening thunderstorms.
While instability will not be as large as farther west over the
Mid-South to southern Great Plains, it will be sufficient to warrant
sporadic occurrences of severe hail and damaging winds eastward to
the coastal Carolinas.

..Grams.. 05/24/2024

$$