Storm Prediction Center Mesoscale Discussion 768

   Mesoscale Discussion 0768
   NWS Storm Prediction Center Norman OK
   0651 AM CDT Mon May 18 2026

   Areas affected...eastern Missouri...far southeast Iowa...and
   west-central Illinois

   Concerning...Severe potential...Watch unlikely 

   Valid 181151Z - 181315Z

   Probability of Watch Issuance...20 percent

   SUMMARY...A long lived thunderstorm cluster has shown signs of
   renewed updraft intensity. An isolated large hail or damaging wind
   gust to two will be possible this morning. A watch is currently not
   expected.

   DISCUSSION...A long lived MCS continues to move east across northern
   and central Missouri this morning. Recent satellite observations
   have shown a renewed cooling trend of cloud tops indicated of
   increasingly robust updrafts. This correlated to an increase in the
   number of taller, stronger updraft cores evident in MRMS CAPPI
   imagery.

   The renewed vigor of some of these updrafts appears tied to a
   slightly better environment across eastern Missouri than farther
   west. MUCAPE values are between 1500-2000 J/kg and objectively
   analyzed effective-layer shear has improved to between 30 and 40
   knots. Additionally, KLSX VAD winds show strong 0-1 kilometer
   veering flow, with around 40-knots of shear. Upper-tropospheric
   winds have also improved as the area is on the northern periphery of
   a 60-knot 300-mb subtropical jet streak lifting northeast across
   Arkansas and Missouri.

   All this will result in the potential for some severe hail and wind
   this morning along the main convective edge of the MCS. Given the
   strength of the low-level flow, a brief tornado cannot be ruled out,
   especially where this MCS intersects the outflow of an earlier MCS.

   There is uncertainty as to the longevity of this threat. Latest CAM
   guidance suggests that as the low-level jet weakens later this
   morning, the overall severity of the MCS will weaken as well.
   However, given the overall character of the environment, the
   potential for isolated severe hail and wind will be possible over
   the next couple of hours.

   Given the sporadic nature and uncertainty regarding the longevity of
   the threat, a watch appears unlikely at this time, but trends are
   being monitored.

   ..Marsh/Gleason.. 05/18/2026

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

   ATTN...WFO...ILX...LSX...DVN...SGF...

   LAT...LON   38389268 38909226 39539180 40379160 41129155 41219082
               41089013 40568959 39768942 39108959 38648979 38159035
               38019113 38129222 38389268 

   MOST PROBABLE PEAK TORNADO INTENSITY...UP TO 90 MPH
   MOST PROBABLE PEAK WIND GUST...55-70 MPH
   MOST PROBABLE PEAK HAIL SIZE...UP TO 1.25 IN