SPC AC 262020

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0320 PM CDT Sun May 26 2024

   Valid 262000Z - 271200Z

   ...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS ACROSS
   SOUTH-CENTRAL AND SOUTHEAST MISSOURI...FAR NORTHEAST
   ARKANSAS...SOUTHERN ILLINOIS...FAR SOUTHWEST INDIANA...WESTERN
   KENTUCKY...AND NORTHWEST TENNESSEE....

   ...SUMMARY...
   Severe storms are expected from the Ozarks this afternoon and
   evening to the Ohio and Tennessee Valley tonight. Tornadoes, some
   strong to intense, and large to very large hail are the primary
   threats this afternoon and evening with an evolving overnight severe
   wind/embedded tornado threat tonight.

   Primary focus of this outlook update was a moderate risk upgrade
   from south-central Missouri into western Kentucky and northwest
   Tennessee. An EML has advected across this region in the wake of
   morning convection which has permitted strong heating and
   destabilization. The outflow boundary and the destabilized region
   north of this boundary provide a vorticity rich low-level airmass
   favorable for tornadoes. Supercells are already starting to develop
   in the hot and unstable airmass across southwest Missouri and will
   move toward this vorticity rich airmass this evening. Additionally,
   a strengthening low-level jet is expected across this area tonight
   which will elongate low-level hodographs. Most members of the 18Z
   and 19Z WoFS show several intense, long track supercells through
   this region later this evening with increased 0-2km UH
   probabilities, giving more supporting evidence for the rapidly
   evolving tornado threat. Given the aforementioned factors, several
   strong to intense tornadoes are possible this evening. See MCD #980
   for additional information about the evolving threat in this region.


   Eventually, these supercells will likely congeal into an MCS which
   amid extreme instability, strong shear, and steep lapse rates, will
   likely have a significant wind threat into the late evening and
   early overnight hours. 

   In addition, added a small marginal risk across southwest South
   Dakota and northern North Dakota where a few stronger storms have
   developed amid weak instability and moderate shear. See MCD 982 for
   additional information about this threat.

   ..Bentley.. 05/26/2024

   .PREV DISCUSSION... /ISSUED 1140 AM CDT Sun May 26 2024/

   ...Ozarks/Arklatex to Ohio/Tennessee Valleys and south-central
   Appalachians...
   Ongoing/long-lived bowing complex, with a history of measured severe
   gusts and wind damage, continues to move east across central
   KY/northern TN at 16z.  The downstream environment continues to
   destabilize as diurnal heating of upper 60s/near 70 def F dewpoints
   continues, and this complex is expected to continue moving east
   through this afternoon while maintaining a risk for damaging gusts
   and embedded QLCS circulations.

   In the wake of this convective system, a pronounced theta-e gradient
   has become established from northern TN westward, becoming more
   diffuse over southern MO, where strong heating is occurring.  Severe
   thunderstorms are forecast to redevelop this afternoon across
   southern MO within a strongly sheared environment characterized by
   50 kts of westerly shear, and strong MLCAPE. Supercell structures
   should be the dominant convective mode for several hours, with a
   risk for all severe hazards including very large hail and strong
   tornadoes. 

   The convective system may congeal with time into more of a linear
   structure, with a risk for all hazards continuing into the overnight
   hours within an amply-sheared and moderately unstable environment.
   The Enhanced Risk has been expanded farther south over portions of
   northern MS/AL/far northwest GA based on 12z HREF calibrated
   guidance.

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