SPC May 16, 2025 1630 UTC Day 1 Convective Outlook

SPC 1630Z Day 1 Outlook

Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
1128 AM CDT Fri May 16 2025

Valid 161630Z - 171200Z

...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS THIS
AFTERNOON/EVENING MIDDLE MISSISSIPPI AND LOWER OHIO VALLEYS...

...SUMMARY...
A regional outbreak of severe thunderstorms is likely this afternoon
into tonight across parts of the mid Mississippi, Ohio and Tennessee
Valleys. This will include intense supercells with strong,
potentially long-track tornadoes and very large hail. The threat for
damaging winds in excess of 75 mph will increase into this evening
as storms grow into larger clusters.

...Mid MS Valley to the Mid-Atlantic through tonight...
An occluded 984 mb cyclone will move slowly eastward toward the
upper Great Lakes and fill through tonight, as a trailing cold front
progresses across MO/IL/IN/MI.  Ongoing thunderstorm clusters will
likely persist through the afternoon along the primary
moisture/buoyancy gradient into the northern Mid-Atlantic, and with
a developing cold pool from TN/KY into VA/NC within the warm sector.
 MLCAPE increasing to 2000 J/kg or greater, steepening low-level
lapse rates, and sufficient deep-layer vertical shear (effective
bulk shear of 40-50 kt) will maintain a mix of embedded supercells
and bowing segments capable of producing very large hail (2 inch
diameter or larger), thunderstorm gusts of 60-75 mph, and a couple
of tornadoes.

Farther west and in the wake of the ongoing TN/KY storms, rapid
recovery is underway across southern MO where moisture advection and
strong surface heating will result in rapid destabilization. 
Visible imagery shows evidence of ascent over northwest AR/southwest
MO that will soon interact with the destabilizing warm sector. 
Supercell development is expected by midday into early afternoon
from south central into east central MO, and storms will
subsequently expand in coverage while spreading quickly
east-northeastward across southern/central IL this afternoon and
into IN late this afternoon/evening.  The initial storms in MO will
likely remain semi-discrete with the potential to producing very
large hail (in excess of 3 inches in diameter) and a couple of
strong tornadoes given very long hodograph with sufficient low-level
shear.  Gradual upscale growth into clusters/line segments is
expected through storm interactions, with an increase in the
potential for swaths of 65-85 mph gusts into this evening.  More
isolated supercell development may also occur later this afternoon
along the modifying outflow boundary into KY, where all hazards are
expected.

...Northern IL into Lower MI this afternoon/evening...
An embedded speed max and associated zone of ascent now over
northern MO will eject quickly east-northeastward toward Lower MI by
early tonight.  The degree of moistening/destabilization will be
modulated by how quickly storms form and how widespread coverage is
this afternoon farther to the south from IL into IN.

...AR into southeast OK and northeast/central TX this afternoon...
Despite some cloud cover, surface heating in cloud breaks is
allowing surface temperatures to warm into the 80s with low-mid 70s
boundary-layer dewpoints, beneath midlevel lapse rates in excess of
8 C/km.  Scattered thunderstorm development is expected this
afternoon along the primary wind shift from AR/southeast OK into
northeast and potentially central TX.  MLCAPE of 3000-4000 J/kg and
long hodographs with strong deep-layer shear will favor supercells
capable of producing very large hail (3-4 inches in diameter) with
the initial discrete storms, and damaging gusts of 60-75 mph.  The
tornado threat is less certain given relatively weak low-level shear
(as a result of the primary mass response/low-level jet into the
TN/OH Valleys), and will likely rely on favorable storm
interactions.

..Thompson/Grams.. 05/16/2025

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