SPC AC 141220
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0720 AM CDT Fri Mar 14 2025
Valid 141300Z - 151200Z
...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS ACROSS THE
MID-MISSISSIPPI VALLEY AND PORTIONS OF THE LOWER OHIO VALLEY AND MID
SOUTH...
...SUMMARY...
A regional outbreak of severe storms is likely across the
Mid-Mississippi Valley to the Lower-Mississippi Valley, including
portions of the Lower Ohio Valley and Mid South. Tornadoes, several
of which could be strong, widespread severe gusts ranging from 60 to
100 mph, and scattered large hail up to baseball size will be
possible.
...Synopsis...
Water-vapor satellite imagery shows a powerful negatively tilted mid
to upper-level shortwave trough over the Four Corners into the
southern High Plains. A very intense 500-mb speed max in excess of
100+ kt will round the base of the trough and quickly move
northeastward across OK this afternoon and near Lake Michigan late
tonight. The associated 12hr mid-level height falls (on the order
of 240-270m) will overspread portions of the central U.S. as a deep
cyclone develops northeast from the central High Plains into the
Upper Midwest. In the low levels, a dryline will surge across the
central Plains eventually arcing from the low southeastward into the
Ozarks.
Strong boundary-layer heating is forecast ahead of the cyclone and
initial storms will likely develop by early afternoon (18-20z) from
eastern NE southward into eastern KS/western MO. Storms will
quickly grow upscale into a fast northeastward-moving band of storms
posing a risk for all hazards as this activity moves into IA and
towards the MO/IA/IL border region. Intense thunderstorm
straight-line gusts peaking locally in the 80-100 mph range are
possible with the stronger cores/inflections in the band as it
matures and moves across the Mid MS Valley and eventually into the
southwestern Great Lakes tonight. Have made some adjustments for
higher wind/tornado probabilities over northern IL eastward into the
Michiana region late tonight.
Additional severe storms will develop southeast along the wind shift
into MO and within the northern periphery of richer low-level
moisture from southeast MO southward into eastern AR and into
northern MS/western TN. Stronger high-level flow over the Mid South
will promote more discrete supercell structures. Recent model
guidance indicates at least widely scattered storms developing
towards the evening as far south as the MS/AR/TN border region.
Forecast soundings strongly favor intense supercells capable of
large to very large hail and potentially a few strong tornadoes this
evening and perhaps continuing into the late evening. Forcing for
ascent will be more nebulous farther south into the Gulf coastal
plain late. However, model guidance continues to suggest at least
isolated supercell development may occur within an increasingly rich
and weakly capped boundary layer overnight. Have likewise extended
10-percent significant tornado probabilities farther south into
southern MS to account for this forecast scenario. Moderate
buoyancy and enlarged hodographs will support a supercell tornado
risk with this activity with it perhaps continuing into early
Saturday morning.
..Smith/Thompson.. 03/14/2025
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