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Mesoscale Discussion 35
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   Mesoscale Discussion 0035
   NWS Storm Prediction Center Norman OK
   0305 AM CST Thu Jan 12 2017

   Areas affected...portions of central and northeast IL...northwestern
   IN...Michiana...and southern Lower MI

   Concerning...Freezing rain 

   Valid 120905Z - 121500Z

   SUMMARY...The onset of freezing rain is expected over central IL
   during the late overnight and move northeastward into portions of
   northern IN prior to sunrise and southern Lower MI this morning. 
   Appreciable freezing rain rates will be spotty with elevated
   convection but may range 0.05-0.10 inch per 3 hours.

   DISCUSSION...Radar mosaic and lightning data around 09 UTC shows an
   expanding precipitation shield near the MO/IL/IA border associated
   with weak elevated thunderstorms.  The activity near the MS river is
   likely associated with the leading edge of stronger mid-level ascent
   /dcva/ associated with a east-northeastward moving shortwave trough
   analyzed over the central Great Plains.  This feature will quickly
   move downstream towards the southern Lake MI vicinity by 15 UTC.  

   In the low levels, surface analysis shows the southeast progression
   of cold air with the freezing line over central IL and far
   southwestern MI.  Low-level cold air advection will result in the
   discussion area falling at or below 32 deg F during the period and
   prior to the beginning of precipitation.  Forecast soundings show
   the thermal stratification of a shallow sub-freezing layer beneath a
   warm layer around H85.  Moderately steep H7-H5 lapse rates around 7
   deg C per km and a saturating profile will yield weak buoyancy
   /100-200 J per kg MUCAPE/.  As a result of the increased forcing for
   ascent and columnar saturation, freezing rain is forecast to begin
   near the MS river and spread downstream to the east-northeast during
   the overnight and early morning.  Forecast soundings also imply the
   heaviest rates will occur in a time window around 11-13 UTC near
   Pontiac, IL, 12-15 UTC near South Bend, IN, and 14-15 UTC near
   Jackson, MI.  Given the convective character of the forecast
   precipitation, spotty amounts are expected but freezing-rain rates
   of 0.05-0.10 inch per 3 hours are possible.

   ..Smith.. 01/12/2017


   LAT...LON   42838379 42548346 42118386 41818499 40948698 39948904
               39739005 39899061 40259094 40759070 41868782 42778526

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