Mesoscale Discussion 1247
   NWS Storm Prediction Center Norman OK
   0102 PM CDT Thu Jun 13 2024

   Areas affected...Much of Lower MI...Northern
   IN...North-Central/Northeast IL

   Concerning...Severe potential...Watch possible 

   Valid 131802Z - 132000Z

   Probability of Watch Issuance...60 percent

   SUMMARY...Thunderstorm coverage is expected to increase this
   afternoon. Some large hail (up to 2" in diameter) and/or damaging
   gusts are possible, and a watch will probably be needed.

   DISCUSSION...Visible satellite imagery has shown increasingly
   agitated cumulus from Lower MI southwestward into north-central IL,
   well ahead of the cold front farther west that extends from central
   Upper MI southwestward into west-central IA. This cumulus is
   coincident with increasing mid to upper level cloudiness, suggesting
   that it is likely in response to modestly increasing large-scale
   ascent attendant to the low-amplitude shortwave trough beginning to
   enter the Upper Great Lakes region. Some convective inhibition
   currently remains present within the airmass across much of the
   region, but gradual destabilization is anticipated throughout the
   afternoon. Destabilization is expected first across Lower MI where
   mid-level temperatures are cooler and greater large-scale ascent is
   anticipated, before gradually moving westward with time as strong
   diurnal heating continues. Thunderstorm initiation will likely
   follow the same pattern, beginning over Lower MI and then expanding
   westward with time. There is a chance that a brief thunderstorm or
   two could develop across northern/northeastern IL first as
   large-scale ascent combines within modest mesoscale ascent along the
   pre-frontal trough. 

   Buoyancy will likely remain modest across Lower MI, with MLCAPE
   likely remaining below 1500 J/kg. Stronger buoyancy is anticipated
   across northern IN and north-central/northeast IL, where dewpoints
   in the mid to upper 60s will help foster MLCAPE over 2000 J/kg.
   Vertical shear is expected to be greatest over portions of northern
   IL and northern IN as well, with effective bulk shear likely
   reaching over 40-45 kt this afternoon. Consequently, the greatest
   severe potential is anticipated across northern IL and northern IN,
   with more isolated coverage expected across Lower MI. Large hail is
   possible with initial development, but relatively high cloud bases
   and steep low-level lapse rates suggest a relatively quick evolution
   to outflow-dominant structures capable of damaging wind gusts. A
   watch will probably be needed across portions of the area to cover
   this severe potential.

   ..Mosier/Gleason.. 06/13/2024

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

   ATTN...WFO...DTX...APX...IWX...GRR...IND...LOT...ILX...DVN...

   LAT...LON   40408796 40338929 40838984 41398996 42108923 42318826
               42458737 42778669 43248639 43868597 44528530 44638427
               43938351 43188334 42458360 41728441 40978570 40408796