SPC AC 251954

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0254 PM CDT Mon Sep 25 2023

   Valid 252000Z - 261200Z

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS THE
   FLORIDA PENINSULA AND SOUTH TEXAS TO SOUTHWEST LOUISIANA...

   ...SUMMARY...
   Isolated severe thunderstorms remain possible across southern parts
   of Texas, southwestern Louisiana, and the Florida Peninsula late
   this afternoon into this evening.

   ...20Z Update...
   No changes have been made to the severe probabilities. Isolated
   strong to potentially severe thunderstorms remain possible across
   parts of the FL Peninsula, and also across southern parts of Texas
   into southwest LA. See the previous discussion below for more
   information. Also see MCD 2196 for more information regarding the
   short-term threat near the upper TX coast.

   ..Dean.. 09/25/2023

   .PREV DISCUSSION... /ISSUED 1130 AM CDT Mon Sep 25 2023/

   ...Southern Texas/southwest Louisiana...
   Multiple areas of widely scattered showers and thunderstorms,
   generally in a weakening/diminishing trend through mid/late morning,
   exist across the region. Additional widely scattered thunderstorm
   development is expected to uptick in coverage and intensity later
   this afternoon, influenced by the southward-sagging front as well as
   several zones of outflow/differential heating. Multicellular storms
   will be common, with some potential for a few supercells
   particularly with westward extent across south-central/southwest
   Texas toward the Rio Grande, where deep-layer shear and buoyancy
   will be a bit stronger and where large hail potential is more
   apparent. This is aside from the potential for isolated severe wind
   gusts that will more broadly exist across the region.

   ...Central/southern Florida...
   Scattered thunderstorms are expected to develop across the region
   this afternoon. Localized strong/severe wind gusts are possible
   along with the possibility of marginally severe hail. This regime is
   the east of upper troughing over the central/northeast Gulf of
   Mexico, with a moist environment (PW 1.75-2.25-inches) existing
   across much of the Peninsula, with sea breeze boundaries focusing
   increasing diurnal thunderstorm development. While deep-layer winds
   will be weak, veering with height will contribute to 20-30 kt
   effective-shear magnitudes, supporting multicellular storm
   organization. Convection should diminish in coverage and strength
   after sunset as a combination of nocturnal cooling and increasingly
   prevalent outflow air stabilizes the boundary layer inland.

   ...Southeast MN/western WI/northeast IA/northwest IL...
   A few funnels may occur this afternoon across the region in relative
   proximity to the southeastward-moving upper low (-16C at 500mb),
   focused near the surface occluded front that will be located near
   the Mississippi River, and generally oriented parallel to it. There
   is where low-level buoyancy including 100-125 J/kg 0-3 km CAPE will
   be maximized with ambient vorticity. While a tornado cannot be
   entirely discounted, the potential for such currently appears to be
   very low, while funnels/briefly strong storms are otherwise
   plausible within the weak vertical shear environment (effective/0-6
   km shear magnitudes less than 20 kt).

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