934
ACUS02 KWNS 181732
SWODY2
SPC AC 181730

Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1230 PM CDT Wed Sep 18 2024

Valid 191200Z - 201200Z

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

...SUMMARY...
Scattered severe thunderstorms are possible from mid-afternoon to
mid-evening on Thursday across central/eastern Minnesota, Iowa, and
western Wisconsin. A few tornadoes, isolated very large hail, and
damaging winds may occur.

...Upper Midwest...
A seasonably strong stacked cyclone initially near the ND/SK/MB
border region is forecast to move northeastward through the period.
An attendant cold front will move eastward through the day across
parts of the upper Midwest and central Plains. Diurnal heating of a
rather moist airmass along/east of the front will support a
relatively narrow zone of moderate to large MLCAPE (1500-3000 J/kg)
by peak heating. Moderate midlevel flow will support sufficient
effective shear for storm organization, with shear vectors generally
aligned perpendicular to the front. This will support supercell
potential from central/eastern MN into western WI and parts of IA,
though the timing of initial development and western extent of the
primary severe threat remain somewhat uncertain.

Favorable instability and an initially discrete storm mode will
support large to very large hail as storms mature, along with some
potential for isolated damaging wind. Low-level hodographs will also
be sufficiently curved/enlarged to support a tornado threat. A
tendency toward clustering and perhaps some modest upscale growth is
possible later in the storm evolution, with a severe threat likely
persisting into the early/mid evening. The threat should begin to
wane by late evening into Thursday night, as instability weakens
with time and eastward extent.

...Eastern KS/northern OK into southeast NE/western MO...
A conditionally favorable storm environment is also expected to
develop from southeast NE into eastern KS/western MO and northern
OK, along/ahead of the approaching front. While storm coverage will
generally be less compared to areas farther north (due to weaker
large-scale ascent), isolated supercells and/or stronger clusters
will be possible from late afternoon into the evening. Increasingly
warm midlevel temperatures will tend to limit updraft intensity with
southward extent, but an isolated severe threat could extend as far
south as northern OK.

..Dean.. 09/18/2024

$$