Storm Prediction Center Mesoscale Discussion 2202

   Mesoscale Discussion 2202
   NWS Storm Prediction Center Norman OK
   0955 PM CST Sun Nov 09 2025

   Areas affected...Northwestern Indiana and northeastern Illinois

   Concerning...Heavy snow 

   Valid 100355Z - 100900Z

   SUMMARY...An intense lake effect snow band will drift slowly
   south-southwestward across northwestern Indiana and northeastern
   Illinois through the early morning hours. Heavy snowfall rates of 2+
   inches/hour are expected under the core of the band.

   DISCUSSION...Regional radar data shows a well-defined snowband
   favorably oriented along the long axis of Lake MI. This snowband is
   on the backside of a mesoscale low that evolved off of Lake MI and
   is moving slowly southward across far northern IN. As this feature
   continues southward, and low-level flow continues veering to a
   north-northeast direction over Lake MI, the band will have a
   tendency to drift gradually south-southwestward across far
   northwestern IN and northeastern IL through the early morning hours.
   The 00Z GRB sounding sampled very cold temperatures aloft (-40C at
   500 mb), which is yielding steep low/midlevel lapse rates and a deep
   convective boundary layer (aided by relatively warm lake waters). 

   Given the favorable/persistent orientation of low-level flow down
   Lake MI and significant convective enhancement, heavy snowfall rates
   of 2-3 inches per hour are expected under the core of the band as it
   continues south-southwestward. Isolated lightning flashes will also
   be possible. There will likely be a sharp drop-off in the heaviest
   snowfall rates as the band tracks southwestward across northeastern
   IL (owing to less favorable thermodynamic conditions), though
   exactly where this will occur is uncertain. Additionally, gusty
   winds within the band will yield significant visibility reductions
   where snowfall rates are maximized.

   ..Weinman.. 11/10/2025

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

   ATTN...WFO...IWX...LOT...

   LAT...LON   42278765 41998745 41768708 41818669 41608645 41248667
               41228727 41438787 42008820 42268810 42358788 42278765