SPC AC 241630

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1130 AM CDT Sat Jun 24 2023

   Valid 241630Z - 251200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS PARTS OF THE UPPER
   MIDWEST TO THE MID-MS VALLEY...

   ...SUMMARY...
   Scattered severe thunderstorms are most likely across portions of
   Minnesota and Iowa into the Mid-Mississippi Valley through this
   evening. Brief tornadoes, large hail, and damaging winds will be
   possible.

   ...Upper Midwest to Mid-MS Valley...
   Remnants of a decaying MCS persist in eastern IA with residual cloud
   cover and convective redevelopment in its wake across central into
   southwest IA. More pronounced insolation has occurred over northwest
   IA and parts of eastern NE. This will likely yield a moderately
   unstable air mass with MLCAPE approaching 2500 J/kg in a few hours.
   Morning guidance is insistent on surface-based thunderstorm
   development occurring by early afternoon, which appears a bit too
   soon given the lingering morning convection/cloudiness, but is
   plausible owing to modest mid-level lapse rates/EML. As such,
   confidence is below-average with regard to timing and evolution of
   this afternoon's severe threat. 

   Downstream of a 60-65 kt 500-mb westerly jetlet centered on NE,
   deep-layer shear will support potential for several supercells. A
   few-hour window for a couple of these to produce tornadoes may
   overlap along the residual outflow boundary before convection likely
   consolidates into clusters and low-level winds become more veered
   into the evening. East to southeast-moving clusters may develop into
   a semi-organized MCS during the evening and yield a strong to
   isolated severe wind threat across the Mid-MS Valley. This activity
   should gradually weaken tonight after eventually outpacing greater
   instability/buoyancy to its west.

   A separate area of lower-topped tornado potential is evident in
   northwest/north-central MN along the surface warm front that will
   extend east of the primary cyclone centered near the northeast
   SD/southeast ND border area. Backed surface winds that veer with
   height will support enlarged low-level hodograph curvature. In
   conjunction with low LCLs, these factors may support a threat for
   brief tornadoes during the late afternoon to early evening. 

   ...West TX to the Ozark Plateau...
   Isolated to scattered high-based thunderstorms will develop during
   the late afternoon to early evening across at least west TX, and
   perhaps across parts of OK this evening into tonight. With a stout
   mid-level anticyclone centered along the Trans-Pecos portion of the
   Rio Grande, deep-layer shear will be progressively stronger with
   northeast extent towards the Ozark Plateau. Sporadic severe gusts
   from microbursts will be the main threat in TX, with a conditional
   threat for isolated severe wind/hail into the Ozark Plateau.

   ...LA vicinity...
   Despite weak low-level shear, a belt of modest mid-level northerlies
   will support potential for an isolated severe wind and hail threat
   as isolated to scattered thunderstorms develop this afternoon within
   the boundary-layer moisture/buoyancy gradient between LA/MS.

   ..Grams/Wendt.. 06/24/2023

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