SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1131 AM CDT Fri May 24 2024
Valid 241630Z - 251200Z
...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS THE
SOUTHERN PLAINS AND PARTS OF THE MIDWEST...
...SUMMARY...
Severe thunderstorms are expected this afternoon and evening from
north Texas/eastern Oklahoma and the Mid-South into the Midwest
including parts of Missouri and Illinois.
...Midwest including parts of IL/MO/southern WI...
A previously intense/well-organized bow echo has weakened into
northeast Illinois/southeast Wisconsin through late morning, with
the gust/outflow boundary extending from the Chicagoland
southwestward into west-central Illinois near/south of the IA/MO/IL
border vicinity. The surface cold pool has considerably impacted the
post-MCS environment, with likely ramifications for the magnitude
and likelihood of the severe risk into far northern
Illinois/Wisconsin, although some measure of air mass recovery will
occur and severe storms will be possible even without a pristine
boundary layer. The region is on the north-northeast periphery of a
substantial elevated mixed layer (EML) sampled by 12z observed
soundings including Topeka KS and Lincoln IL.
The outflow boundary where it intercepts the approaching cold front,
in general vicinity of the IA/MO/IL border, will likely be a favored
zone for renewed severe storm development later this afternoon. Some
initial supercell development can be expected before subsequent
upscale growth by evening, with all severe hazards plausible in this
corridor.
Farther north, across far eastern Iowa/northern Illinois into
southern Wisconsin, later-day severe potential is a bit more
uncertain owing to this morning's MCS. However, at least isolated
severe storms capable of severe hail/damaging winds may occur near
the eastward-advancing cold front pending the degree of air mass
recovery/destabilization.
...Southern Plains including North TX/Eastern OK to Mid-South...
Scattered thunderstorms, including locally intense supercells, are
expected to develop into mid/late afternoon mainly near the
southwest/northeast-oriented front, with more isolated near-dryline
development possible into central Texas. After initial supercells,
updraft growth is likely given the strong surface heating, abundant
moisture (70s F dewpoints common), steep deep-layer lapse rates and
intense buoyancy (4000-5000 J/kg MLCAPE).
Low-level flow and hodograph size will be modest. However, ambient
mid/upper winds will be strong enough to support supercells (left-
and right-moving), with effective-shear values near 50 kt. Large to
very large hail should be common in the first few hours after
initiation, and locally severe gusts are expected as well. In the
wake of predawn MCS, airmass recovery is expected into southeastern
and east-central Oklahoma in the zone of warm/moist advection ahead
of the front. A relatively dense and enhanced concentration of hail
potential from eastern Oklahoma into north-central Texas is
expected, with hailstones greater than 2 inches in diameter likely,
and some hail perhaps exceeding 3 inches. Otherwise, deep,
precip-loaded downdrafts will provide most of the wind potential
early, with some upscale clustering and cold-pool aggregation
possible to maintain damaging-wind potential into late evening,
before activity generally weakens.
...Southeast States...
Isolated severe thunderstorms are possible mainly this afternoon
through early evening from the southern Appalachians vicinity/north
Georgia to the coastal Carolinas. Steepening low-level lapse rates
and ample buoyancy will support strong updrafts/downdrafts, with a
modestly enhanced belt of mid-level westerlies contributing to
multicell sustenance.
..Guyer/Squitieri.. 05/24/2024
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