Storm Prediction Center Mesoscale Discussion 818

   Mesoscale Discussion 0818
   NWS Storm Prediction Center Norman OK
   0534 PM CDT Thu May 21 2026

   Areas affected...portions of central and south-central Texas

   Concerning...Severe potential...Watch unlikely 

   Valid 212234Z - 220000Z

   Probability of Watch Issuance...20 percent

   SUMMARY...Some potential for damaging wind gusts and large hail will
   persist for at least another couple of hours. Watch issuance remains
   unlikely.

   DISCUSSION...Widely scattered thunderstorms remain ongoing in close
   proximity to a southward surging, convectively-reinforced surface
   boundary. Locally greater effective shear of 25-35 kts is supporting
   some updraft organization within this corridor, with marginal
   supercell structures evident in latest radar imagery in addition to
   a bowing segment/cluster noted in Gillespie/Llano Counties.
   Expectation is for this activity to gradually shift to the south and
   east in conjunction with the aforementioned surface boundary.
   Moderately steep mid-level lapse rates and MLCAPE of 1500-2500+ J/kg
   will continue to support a threat for isolated large hail with
   strong to occasionally damaging wind gusts also possible.

   Locally greater severe potential may accompany a bowing cluster as
   it progresses eastward toward the Austin, Texas, vicinity. A
   separate corridor of locally greater severe potential also appears
   possible farther west as southeastward-moving convection encounters
   greater instability (noted in latest objective analysis) within a
   zone of steeper low- and mid-level lapse rates in the vicinity of
   Del Rio. The overall severe risk is expected to remain limited in
   coverage/magnitude. Thus, watch issuance remains unlikely at this
   time. Trends will continue to be monitored, however.

   ..Chalmers/Thompson.. 05/21/2026

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

   ATTN...WFO...FWD...EWX...SJT...

   LAT...LON   30210162 30710146 30910112 30890049 30640002 30529947
               30629900 31049860 31249826 31389792 31299757 31039732
               30719728 30229732 29649760 29439815 29289890 29250003
               29270057 29400106 29670140 29830153 30210162 

   MOST PROBABLE PEAK WIND GUST...55-70 MPH
   MOST PROBABLE PEAK HAIL SIZE...1.00-1.75 IN