Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0700 AM CST Sun Dec 28 2025
Valid 281300Z - 291200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM EASTERN
ILLINOIS TO INDIANA...
...SUMMARY...
Scattered severe thunderstorms are possible over Illinois and
Indiana this afternoon through the evening. Severe wind gusts
capable of wind damage and a couple of tornadoes are the primary
threats.
...Mid MS Valley east through IN-OH-western PA...
Water-vapor imagery this morning shows a mid-level low near the
MT/ND border with a trough into the central Rockies/Sangre de
Cristos. This mid-level low will move into the central Great Lakes
by early Monday morning. Strong southwesterly 500-mb flow (80 kt)
extending from the base of the trough through the lower MO Valley
and OH Valley will feature an intensifying 110-kt jet reaching the
MO-IL border this evening before further strengthening to 130 kt
over OH by the end of the period.
A surface low over eastern KS will deepen rapidly through tonight as
it moves to Lake Huron. A frontal zone extending east-northeast
through the southern Great Lakes this morning will serve as the
northern edge of the moist sector. A cold front initially over
KS-OK will surge south-east. Southerly low-level flow across the
moist sector will maintain a fetch of seasonably high 58-62 deg F
dewpoints immediately ahead of the front/low.
A rain shield with embedded thunderstorms this morning from northern
MO into the southern Great Lakes could feature a stronger storm or
two through midday, but the primary severe risk will likely focus
this afternoon through tonight. Model guidance indicates the cap
will erode near the evolving triple point and cold front by mid-late
afternoon. Upwards of 500-1000 J/kg MLCAPE is possible across parts
of central into eastern IL with buoyancy tapering with east extent
across the OH Valley. A southward-developing convective band is
forecast to evolve late this afternoon through the early evening.
Long hodographs and strong 2-3 km flow will favor a risk for severe
gusts with the more intense storms and surges with the maturing
band. Models indicate the wind-damage threat may persist across the
OH Valley/southern Great Lakes tonight despite meager instability.
The tornado risk appears highest with cells that can develop near
the instability axis and mature before either destructive
interference of the larger-scale cold pool overwhelms cellular mode,
and/or this activity moves farther east into lessening instability.
..Smith/Weinman.. 12/28/2025
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