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Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
0745 AM CDT Wed Mar 19 2025

Valid 191300Z - 201200Z

...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS THIS
AFTERNOON/EVENING FOR PARTS OF CENTRAL/NORTHERN ILLINOIS AND WEST
CENTRAL INDIANA...

...SUMMARY...
Scattered severe thunderstorms are possible this afternoon/evening
from central/northern Illinois to western Indiana.  A few tornadoes,
large hail, and damaging wind gusts will be possible.

...IL/IN this afternoon into early tonight...
A deep (989 mb) cyclone near the northeast KS/northwest MO border
will move northeastward to northern IL by this evening and Lower MI
overnight, in conjunction with a deep midlevel trough and 100+ kt
midlevel jet streak.  Elevated convection is ongoing this morning in
a zone of focused ascent with warm advection/frontogenesis across
IA, where isolated large hail may occur with MUCAPE around 500 J/kg
and steep midlevel lapse rates/cool midlevel temperatures.  The warm
sector of the cyclone is characterized by a narrow/modest corridor
of returning moisture (low-mid 50s boundary-layer dewpoints) that
will overspread MO/IL through the afternoon.  Surface heating in
cloud breaks, continued moisture advection and relatively cool
midlevel temperatures will all contribute to warm sector
destabilization (MLCAPE 500-750 J/kg) through the afternoon across
IL.

Surface-based thunderstorm development will beco*e probable by
early-mid afternoon in a broken band along and just ahead of a
remnant dryline moving from MO into IL, and storms will subsequently
move eastward/northeastward into IN by early tonight before
weakening gradually.  The deeper buoyancy profiles will be on the
cyclonic side of the midlevel jet, where 500 mb temperatures will be
< -20 C. Forecast wind profiles suggest supercell potential with
long hodographs (effective bulk shear vectors >50 kt), and
sufficient low-level hodograph curvature/shear for tornado
potential.  The primary uncertainty centers of the degree of
low-level moistening/destabilization, and the current forecast
represents a conditional/reasonable worst case scenario.  Otherwise,
occasional large hail (1-1.5 inches in diameter) will be possible in
IL this afternoon/evening, and the threat for damaging gusts (60-70
mph) and a couple of tornadoes will persist into IN through early
tonight.

...TN/MS/AL this afternoon/evening...
Boundary-layer dewpoints will slowly increase to the upper 50s/lower
60s ahead of the surface wind shift moving across AR/LA this
afternoon.  Forcing for ascent should be sufficient to remove the
cap, allowing some deep convection in a broken band this
afternoon/evening.  Buoyancy will be relatively weak co*pared to the
vertical shear, so it will be difficult to get sustained severe
storms and isolated wind damage will be the most probable threat.

..Thompson/Dean.. 03/19/2025