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Mesoscale Discussion 1294
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   Mesoscale Discussion 1294
   NWS Storm Prediction Center Norman OK
   0833 AM CDT Wed Jul 12 2017

   Areas affected...Chicago...northern Indiana...southwest Lower
   Michigan...far northwest Ohio

   Concerning...Severe potential...Watch unlikely 

   Valid 121333Z - 121530Z

   Probability of Watch Issuance...20 percent

   SUMMARY...Isolated strong to locally severe gusts are possible this
   morning.  There is uncertainty regarding the coverage of damaging
   gusts.  The current thinking is much of the activity will remain
   subsevere as it moves east-southeast across the Michiana region.

   DISCUSSION...Radar mosaic shows 2 convective lines---the first near
   the WI/IL border and another over northeast IL and southern Lake
   Michigan.  The airmass downstream of these thunderstorm lines is
   characterized as weakly unstable with 500-1000 J/kg MLCAPE and
   surface temperatures ranging from the lower 70s degrees F over
   southern MI to the upper 70s in north-central IN.  A 37-kt gust was
   measured by the Madison, WI ASOS at 1218Z and gusts generally below
   30-kt were measured over northeast IL with passage of the first
   convective line.

   KMKX VAD data is currently sampling a mature rear inflow jet (50-kt
   from 3 km AGL) over southern WI.  Despite the moist/marginally
   unstable environment downstream of the MCSs, the well organized
   character and dynamic processes therein may augment and increase the
   threat for damaging winds from an otherwise low risk.  Will monitor
   convective trends over the next 1-2 hours.

   ..Smith/Grams.. 07/12/2017

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

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

   LAT...LON   41378742 41888820 42298669 42418532 42088448 41528440
               41268488 41378742 

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Page last modified: July 12, 2017
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