Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0252 PM CDT Tue May 20 2025
Valid 202000Z - 211200Z
...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FOR PORTIONS OF
THE MID MS VALLEY TO THE CENTRAL APPALACHIANS...
...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.
...20Z Update...
Much of the previous forecast remains on track. Earlier storms
across the TN Valley have matured into a QLCS, which is now
approaching the central Appalachians. These storms should progress
toward the eastern extent of a buoyant warm sector with a continued
risk of damaging gusts and perhaps a couple of tornadoes. Storms
poised to cross the MS River over the central MS Valley, and more
discrete storms farther east over western TN/northern MS, should
intensify further as they move eastward amid a strongly sheared and
unstable airmass. The more intense, discrete storms will be capable
of large to very large hail and at least isolated tornadoes. The
more dominant supercells that move into northeast MS, middle TN, and
southern KY, where surface is flow is relatively more backed, will
have the best chance at producing a strong tornado. Lastly, storms
should continue to intensify ahead of a surface low over central IL
and immediate surrounding areas. Shear/buoyancy over this region
favors supercell structures with a continued large hail/tornado
risk.
..Squitieri.. 05/20/2025
.PREV DISCUSSION... /ISSUED 1115 AM CDT Tue May 20 2025/
...KY/TN...
Thunderstorms are ongoing across central KY/middle TN. These storms
will progress eastward through the afternoon into a moist and
increasingly unstable air mass over eastern KY/TN and eventually
into western WV/VA. Most model guidance suggests that storms will
intensify through the day, with an increasing risk of damaging wind
gusts and a few tornadoes. Refer to MCD #902 for further details.
...AR into the TN Valley this afternoon/evening...
In the wake of the aforementioned convection, rapid heating is
occurring across eastern AR/west TN/northern MS. Surface dewpoints
in the upper 60s to 70s and steep mid level lapse rates will yield
afternoon MLCAPE values around 3000 J/kg and only a weak cap. This
will lead to the development of multiple clusters of intense
thunderstorms (including supercells) that will track eastward
through the afternoon and evening hours. The initial storms will
pose a risk of very large hail and a few tornadoes. As the activity
progresses eastward, the risk of damaging winds will increase with a
persistent risk of tornadoes. Strong tornadoes will be possible.
Storms are expected to get as far east as northwest GA tonight
before slowly weakening.
...MO/IL...
Satellite imagery shows a well-defined shortwave trough and
associated surface low over IA/MO. Ahead of this feature, southerly
low-level winds have transported mid 60s dewpoints into central IL,
where strong heating is now occurring. This will result in moderate
CAPE across the region and encourage rapid thunderstorm development
over northeast and east-central MO by mid-afternoon. Steep lapse
rates aloft and favorable deep-layer shear will support supercell
structures capable of large hail, damaging winds, and a few
tornadoes. Storms will track across IL and into central IN this
evening.
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