Mesoscale Discussion 0243
   NWS Storm Prediction Center Norman OK
   1121 AM CDT Wed Mar 19 2025

   Areas affected...central Illinois

   Concerning...Severe potential...Watch possible 

   Valid 191621Z - 191845Z

   Probability of Watch Issuance...60 percent

   SUMMARY...A gradual intensification of thunderstorm activity is
   likely across parts of southeastern Iowa into west central into
   central Illinois through 1-3 PM CDT.  This may include increasing
   potential for a couple of tornadoes, severe hail and locally strong
   surface gusts.  Trends are being monitored for the possibility of a
   watch, which appears more probable across parts of central/eastern
   Illinois later this afternoon.

   DISCUSSION...Scattered, modest convective development has been
   occurring to the east-northeast of a deep, occluding cyclone now
   centered north of Kansas City.  This has been focused along a
   dryline, which may continue to become better defined into early
   afternoon, as the Rapid Refresh suggests that the trailing cold
   front may not quite overtake it.  The leading edge of the primary
   cooling at mid-levels is contributing to steepening lapse rates
   along the dryline and, with a gradual moistening (surface dew points
   increasing through the lower 50s) of the boundary-layer ahead of it,
   appreciable further destabilization is expected.  It appears that
   this may include mixed-layer CAPE increasing to 500-1000 j/kg in a
   corridor from near the triple point across the southeastern Iowa
   vicinity into central Illinois.

   As this occurs, initially scattered, low-topped thunderstorm
   development is likely to undergo a gradual intensification, beneath
   an intense south-southwesterly mid/upper jet.  Low-level hodographs
   remain rather modest to weak, and Rapid Refresh forecast soundings
   suggest that this may not change much until later this afternoon
   across parts of east central Illinois (roughly near/east of the
   Bloomington and Decatur vicinities).   However, it is possible that
   ambient vertical vorticity and steepening low-level lapse rates
   along the dryline, near the triple point, may support potential for
   at least a couple of generally brief/weak tornadoes, in addition to
   severe hail and locally strong surface gusts.

   ..Kerr/Leitman.. 03/19/2025

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

   ATTN...WFO...LOT...ILX...LSX...DVN...

   LAT...LON   41469066 41088906 38938848 38998954 39438987 39639122
               40889185 41469066