Storm Prediction Center Mesoscale Discussion 1890

   Mesoscale Discussion 1890
   NWS Storm Prediction Center Norman OK
   1053 PM CDT Sun Aug 09 2026

   Areas affected...northern Illinois

   Concerning...Severe Thunderstorm Watch 550...

   Valid 100353Z - 100600Z

   The severe weather threat for Severe Thunderstorm Watch 550
   continues.

   SUMMARY...Severe potential continues within WW550.

   DISCUSSION...Supercells and supercell hybrid clusters continue
   across portions of northern Illinois. As the low-level jet has
   strengthened, a few low topped supercells have shown weak rotation.
   One supercell in Lee County near the warm front/outflow boundary
   across northern Illinois approached 60 kft with more pronounced and
   long lived rotation and reports of a tornado. VAD profiles from KLOT
   are sampling 0-3 km SRH around 350-400 m2/s2, with weakening flow
   above 3 km. Given the favorable low-level shear, transient weak
   rotation will likely continue with low topped cells south of the
   boundary. Any storm that can anchor to the boundary may have
   potential for a tornado in the short term. Mode is becoming more
   clustered through time, with increasing damaging wind potential
   later into the overnight.

   ..Thornton.. 08/10/2026

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

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

   LAT...LON   41999078 42238963 42288892 42228818 42088774 41878733
               41458738 40908815 40758899 40748977 40889035 41209084
               41579095 41999078 

   MOST PROBABLE PEAK TORNADO INTENSITY...85-110 MPH
   MOST PROBABLE PEAK WIND GUST...55-70 MPH
   MOST PROBABLE PEAK HAIL SIZE...UP TO 1.25 IN