ACUS01 KWNS 262002
SWODY1
SPC AC 262000

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0300 PM CDT Thu Mar 26 2026

Valid 262000Z - 271200Z

...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FROM CENTRAL
ILLINOIS EASTWARD INTO INDIANA...OHIO...AND EXTREME WESTERN PENNSYLVANIA...

...SUMMARY...
Scattered severe thunderstorms are expected late this afternoon and
evening across parts of the Midwest and Ohio Valley. Large to very
large hail, a few tornadoes, and damaging winds will all be possible.

...From northern MO across IL, IN, OH and into western PA...

The air mass continues to heat and destabilize this afternoon ahead
of a cold front, which extends from southern Lower MI westward
toward the MO/IA border at 20Z. The air mass remains capped for
surface-based parcels, but clouds will continue to develop along the
boundary with eventual severe storm development along and behind
much of the front. Stronger heating / larger temp-dew spreads
suggest a lesser tornado risk for western areas, while farther east
conditions appear a bit more favorable with more low-level SRH /
with lake breeze effects. GPS water vapor sensors also show higher
values of PWAT over southern IN and KY which will lift northeastward
across IN/OH/PA later today.

In all areas, steep lapse rates aloft and strong deep-layer shear
beneath northwest flow aloft will support supercells producing
damaging hail. This may occur in both elevated cells north of the
undercutting front, and ahead of it.

For more information see mesoscale discussion #0291.

..Jewell.. 03/26/2026

.PREV DISCUSSION... /ISSUED 1108 AM CDT Thu Mar 26 2026/

...Mid Mississippi Valley into the Midwest/Ohio Valley...

Water-vapor imagery late this morning shows a flattened upper ridge
centered over the south-central U.S. with strong westerly
mid/upper-level flow across the Midwest/Great Lakes. A mid-level
shortwave trough over the northern Rockies will move quickly
east-southeast into the Upper Midwest and act to suppress mid-level
heights across the Midwest/Great Lakes through tonight. Surface
analysis this morning showed a weak low over eastern IA with a
west-east oriented frontal zone extending east across the southern
Great Lakes. If a weak surface reflection is maintained and
develops east across the southern Great Lakes through this evening,
it may notably influence severe potential within a focused corridor
late this afternoon through this evening. The aforementioned front
will gradually push south and serve as the primary impetus for storm development.

Beneath a capping inversion, moistening will continue with surface
dewpoints rising into the 56-62 deg F range from the mid MS Valley
east into western PA. Upwards of 500-1500 J/kg MLCAPE is likely by
mid afternoon south of the front. A belt of strong, westerly 50-65
kt 700-mb flow is forecast to move from IA and expand spatially
across the warm sector through early evening. This increase in flow
will act to elongate hodographs despite mainly veered southwesterly
surface flow. Recent convection-allowing model guidance varies
considerably on the depiction of cellular versus mostly linear
clusters evolving in the first few hours of the convective life
cycle. Time-lagged HRRR would imply a more spatially and
numerically extensive supercell hail and tornado risk than most of
the 12z HREF HRW members showing less risk of these hazards. The
tornado risk could focus with potential supercells near a weak low
and where surface flow would locally back to southerly. However,
confidence is muted regarding this specific scenario.

Regardless, current expectations are for thunderstorms to quickly
develop along the length of the front from central IL eastward into
IN, southern Lower MI, and northern OH by 19-22Z as diurnal heating
erodes lingering convective inhibition. A mix of supercells and
organized linear clusters will evolve with large to very large hail
possible. A fairly quick transition to more linear structures
appears likely given the frontal forcing, with an increasing threat
for scattered to numerous severe/damaging winds as one or more
clusters spreads east-southeastward across much of the OH Valley
into western/central PA through the late afternoon and evening.
Given the forecast strength of the low to mid-level flow, isolated
gusts of 75+ mph may occur. There is a threat for a few tornadoes
as well with both supercells and embedded mesocirculations within
the linear clusters.

Farther west across the mid MS Valley (MO into eastern KS), there is
lower confidence in warm sector thunderstorm development this
afternoon and evening due to the presence of a stronger cap.
However, elevated convection may occur along/behind the cold front
this evening, with strong deep-layer shear and sufficient MUCAPE
conditionally supporting supercells with mainly a threat for large
hail.

$$

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