Storm Prediction Center Mesoscale Discussion 1456

   Mesoscale Discussion 1456
   NWS Storm Prediction Center Norman OK
   0740 PM CDT Thu Jul 02 2026

   Areas affected...Northeast Illinois

   Concerning...Severe potential...Watch possible 

   Valid 030040Z - 030245Z

   Probability of Watch Issuance...40 percent

   SUMMARY...Thunderstorms developing across northeast Illinois may
   pose a risk of large hail and damaging winds through the late
   evening hours. Watch issuance is possible if T-storm
   coverage/intensity sufficiently increases.

   DISCUSSION...The early stages of thunderstorm development are noted
   along a subtle low-level confluence band across northeast IL and
   into extreme southeast WI. This confluence band remains just ahead
   of a more prominent outflow boundary quickly approaching from the
   west. The pre-outflow environment over the greater Chicago area was
   recently sampled by an ACARs sounding out of Midway, which depicted
   a largely uncapped and buoyant, but only modestly sheared,
   environment. However, an upstream 00 UTC RAOB from DVN (taken ahead
   of the outflow boundary) sampled stronger (40 knot) mid-level flow
   that is likely approaching the region. 

   Based on these observations, there is reason to expect some degree
   of storm organization in the coming hours across northeast IL as the
   stronger mid-level flow spreads east. Emerging convection will
   likely trend towards clusters with time given the orientation of the
   zone of initiation with the mean flow, but a supercell or two
   appears possible - both ahead of and along/behind the primary
   outflow boundary - in the next few hours. Guidance continues to
   handle this regime poorly, and it's unclear if convection will
   intensify to severe limits before reaching the Lake Michigan shore.
   Nonetheless, trends will be monitored, and watch issuance is
   possible if the severe threat appreciably increases.

   ..Moore/Guyer.. 07/03/2026

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

   ATTN...WFO...LOT...MKX...DVN...

   LAT...LON   41398901 41568941 42058951 42418957 42638923 42778849
               42798767 42528767 42308771 42118762 41998752 41868746
               41768748 41398750 41398901 

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