SPC AC 251630

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1130 AM CDT Sun Jun 25 2023

   Valid 251630Z - 261200Z

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS PARTS OF THE
   MIDWEST/CENTRAL OH VALLEY TO THE MID/DEEP SOUTH...

   ...SUMMARY...
   Scattered to numerous severe storms are expected through tonight
   across a broad portion of the Midwest/Ohio Valley into the Mid and
   Deep South. The greatest threat for tornadoes, at least a couple of
   which could be strong, appears to be in the eastern Indiana, western
   Ohio, and northern Kentucky vicinity during the late afternoon to
   early evening.

   ...Central Great Lakes/OH Valley to the Mid/Deep South...
   Shortwave trough over the Upper MS Valley will shift east into Lower
   MI tonight. Attendant surface cyclone will similarly track east from
   west-central WI into west-central Lower MI. Arcing cold front will
   have greater eastward advancement across parts of the Midwest, with
   trailing portion drifting south-southeast across the Mid-South. A
   broad swath of severe potential remains evident ahead of this front,
   likely yielding scattered areas of severe storms and embedded
   mesoscale corridors of more numerous reports.

   Ongoing convection persists across southeast KY into middle/eastern
   TN and will probably continue along the gradually eastward-shifting,
   north/south-oriented MLCAPE gradient. An isolated damaging wind
   threat should exist downstream across the southern Appalachians. A
   scattered wind/hail threat may emerge within multicell clusters that
   can regenerate westward later this afternoon over the TN Valley and
   persist into this evening.

   Potential for more numerous severe events appears to be focused
   within two bimodal corridors along/ahead of the front. The first is
   in the vicinity of eastern IN/western OH/northern KY border.
   Scattered thunderstorms will increase during the next few hours in
   the Lake MI vicinity arcing south across IN and then southwest
   across the Lower OH Valley. In the wake of the morning convection in
   KY, trailing outflow appears to have finally stalled across western
   KY and far southwest IN. How far to the northeast recovery can occur
   in its wake is uncertain, but it is plausible that it may be able to
   reach the IN/OH/KY border area by late afternoon/early evening. With
   a plume of mid 70s surface dew points to the west of this outflow,
   large buoyancy with MLCAPE of 3000-3500 J/kg will become common.
   Despite gradual weakening of the strong mid-level jetlet attendant
   to the shortwave trough, the leading edge of 50+ kt 500-mb
   westerlies should overlay the Lower OH Valley portion of the front.
   This setup will likely yield the best CAPE/shear/SRH parameter space
   near the IN/OH/KY border area where a few intense supercells are
   expected, capable of producing strong tornadoes and destructive
   hail/wind. Quicker upscale growth into clusters/QLCS is expected
   with northern extent where deep-layer wind profiles will be less
   favorable for maintaining discrete supercell structures. This
   activity should eventually outpace/become pinched off from the large
   buoyancy plume emanating from the Lower OH Valley.

   A second area of potentially destructive hail and wind should
   emanate along the AR portion of the front. The 12Z LZK sounding had
   a very favorable thermodynamic profile with a mean-mixing ratio of
   18 g/kg and mid-level lapse rates of 8-8.5 C/km. With 74-77 F
   surface dew points common to the south of the front, very large
   buoyancy of 3500-4000 J/kg will be prevalent by late afternoon.
   Scattered thunderstorms will develop across northern AR and quickly
   become supercells within the gradient of mid/upper
   west-northwesterly flow. This type of orientation semi-parallel to
   the front should support upscale growth during the evening. Most
   morning CAMs are consistent in suggesting an MCS will evolve
   southeast across the Lower MS Valley with an enhanced threat for
   damaging winds.

   ..Grams/Squitieri.. 06/25/2023

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