SPC May 20, 2025 1300 UTC Day 1 Convective Outlook

SPC 1300Z Day 1 Outlook

Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
0739 AM CDT Tue May 20 2025

Valid 201300Z - 211200Z

...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS MID/DEEP SOUTH
TO TN VALLEY AND CUMBERLAND PLATEAU...

...SUMMARY...
Multiple rounds of severe thunderstorms are expected today through
this evening, centered on the Mid/Deep South, Tennessee/Lower Ohio
Valleys, and Cumberland Plateau. Tornadoes, some of which could be
strong, along with scattered to widespread damaging winds, and large
to isolated significant severe hail will be possible.

...Mid/Deep South to the TN/Lower OH Valleys and Cumberland
Plateau...
Water-vapor imagery this morning shows a negatively tilted,
large-scale mid to upper-level trough centered over the Dakotas
southeastward through the mid MS Valley and Ozarks.  Several
thunderstorms clusters are ongoing within a larger corridor of
convection from the OH Valley southwestward into the lower MS
Valley.  This activity is occurring to the east/southeast of a
gradually filling cyclone forecast to move from the lower MO Valley
eastward into the southwest Great Lakes by late tonight.  

Little change was made to the previous outlook due in part to
general consistency in model guidance and observational trends noted
this morning.  Richer low-level moisture from west-central KY
southward into the Gulf Coast states will contribute to a moderate
to very unstable airmass by the early afternoon in areas void of
recent convective outflow and associated cloud debris.  Scattered to
numerous thunderstorms are forecast to develop coincident with the
diurnal heating cycle.  Forecast hodographs coupled with progged
buoyancy will support a mix of supercells and line segments this
afternoon.  The initial supercell activity will potentially yield a
threat for large to very large hail.  It appears the greatest risk
for supercell tornadoes may exist from northern MS
east-northeastward into middle TN.  Morning convection and
associated destabilization concerns preclude higher tornado risk
probabilities.  However, models continue to indicate upscale growth
into several bands will occur late this afternoon through the late
evening as storms move east across the Enhanced (level 3) Risk area.
Have enlarged severe/damaging wind probabilities across AL/GA to
account for confidence in a continuation of a wind threat persisting
through the evening.  

...IL/IN...
Within the left-exit region of a cyclonically curved mid to upper
speed max, a dry slot and attendant corridor of steep lapse rates
will likely evolve across portions of MO to IL/IN from midday into
the afternoon.  Destabilization will likely be less across the mid
MS Valley eastward into IN, with the richer moisture confined south
of residual outflow and warm frontal zone over the lower OH Valley. 
Nonetheless, isolated to scattered severe thunderstorms are possible
later today into the evening via a mix of shorter-lived supercells
and organized multicells.  Isolated to scattered coverage of severe
and all hazards are possible with the stronger storms before this
activity diminishes during the evening.

..Smith/Marsh.. 05/20/2025

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