Mesoscale Discussion 0376
   NWS Storm Prediction Center Norman OK
   0828 AM CDT Tue Apr 13 2021

   Areas affected...portions of central/southern LA.

   Concerning...Severe potential...Watch possible 

   Valid 131328Z - 131530Z

   Probability of Watch Issuance...40 percent

   SUMMARY...Potential will increase through midday for severe
   thunderstorms across the discussion area, with hail initially the
   main concern.  Damaging wind may become more of a threat with time
   over south-central LA as the thunderstorms become better-organized
   and shift southeastward.

   DISCUSSION...Scattered thunderstorms in clusters have developed
   during the past hour, mainly over portions of Beauregard, Allen,
   Evangeline, and St. Landry Parishes, with a detached, loosely
   organized arc of weaker convection farther north in central LA.  The
   main threat will be large hail for the next couple hours, but
   late-morning/midday evolution into a cold-pool-driven MCS is
   possible with strong-severe gusts.

   This activity currently is occurring in a zone of elevated warm
   advection and moisture transport, north of a marine/warm front
   analyzed over southeast TX and extreme southern LA near a
   HOU-LCH-HUM line.  The 12Z LCH sounding, along that front, sampled
   the upstream inflow layer well for the convection, with steep
   midlevel lapse rates and rich low-level moisture (around 1.75 inch
   PW and surface dew points in the low 70s F).  This supports MLCAPE
   around 1000-2000 J/kg, and MUCAPE around 3000 J/kg, combining that
   sounding with objective mesoanalyses.  Farther north, modifying the
   sounding, the shallow stable layer at LCH will be more pronounced,
   but with favorable MUCAPE values until buoyancy diminishes in
   central/northern LA.  Vertical shear is modest (only around 30 kt
   effective-shear magnitudes and weal low/midlevel flow), so mode
   should remain mainly multicellular and clustered.

   Though earlier than most progs have depicted during the prior
   overnight period, this activity may be the start of the eventual MCS
   that begins forward-propagating southeastward toward the slowly
   northward-moving warm front, with progressively more access to
   surface-based effective inflow parcels in that event.

   ..Edwards.. 04/13/2021

   ...Please see www.spc.noaa.gov for graphic product...

   ATTN...WFO...LIX...LCH...

   LAT...LON   30249243 30669329 31179336 31349247 30919157 30199038
               29629064 29689142 30249243