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Mesoscale Discussion 1470
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   MESOSCALE DISCUSSION 1470
   NWS STORM PREDICTION CENTER NORMAN OK
   0543 PM CDT SAT JUL 18 2015

   AREAS AFFECTED...NRN IL THROUGH NRN IND AND SWRN LOWER MI

   CONCERNING...TORNADO WATCH 436...438...

   VALID 182243Z - 190015Z

   THE SEVERE WEATHER THREAT FOR TORNADO WATCH 436...438...CONTINUES.

   SUMMARY...THREAT FOR STRONG TO SEVERE STORMS PERSISTS FROM NRN IL
   THROUGH NRN IND AND SWRN LOWER MI. THE BEST THREAT FOR A FEW
   TORNADOES APPEARS TO BE FROM NCNTRL THROUGH NERN IND INTO SWRN LOWER
   MI.

   DISCUSSION...EARLY THIS EVENING A CONVECTIVE OUTFLOW BOUNDARY
   EXTENDS FROM NERN IND NWWD INTO NWRN IND WHERE IT INTERSECTS ANOTHER
   OUTFLOW BOUNDARY EXTENDING FROM NWRN IND THROUGH NRN IL. THE
   ATMOSPHERE REMAINS VERY UNSTABLE IN VICINITY OF AND TO THE SOUTH OF
   THESE BOUNDARIES WITH 3000-4000 J/KG MLCAPE. IT APPEARS THE BEST
   TORNADO POTENTIAL NEXT COUPLE HOURS WILL BE FROM NRN IND TO SWRN
   LOWER MI WHERE EFFECTIVE STORM RELATIVE HELICITY IS MAXIMIZED
   /150-200 M2/S2/ JUST ON THE COOLER SIDE OF THE OUTFLOW BOUNDARY.
   DESPITE A PROPENSITY FOR THE STORMS TO GROW UPSCALE...EMBEDDED
   SUPERCELL STRUCTURES WITH LOW-LEVEL MESOCYCLONES ARE POSSIBLE AS THE
   STORMS INTERACT WITH BOUNDARY FROM SWRN LOWER MI INTO NRN IND. 

   SOME SEVERE THREAT PERSISTS FARTHER WEST ACROSS NRN IL BUT IS MORE
   CONDITIONAL. A FEW ENHANCED CUMULUS PERSIST ALONG THIS PORTION OF
   THE OUTFLOW BOUNDARY...BUT LOW-LEVEL WINDS HAVE VEERED AND THIS AREA
   IS LIKELY EXPERIENCING SOME DEEPER SUBSIDENCE IN WAKE OF LEAD
   SHORTWAVE TROUGH. THESE FACTORS ALONG WITH ONSET OF NOCTURNAL
   COOLING LOWERS CONFIDENCE IN ADDITIONAL DEVELOPMENT IN THIS AREA.

   ..DIAL.. 07/18/2015


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

   LAT...LON   41608730 41898659 42448623 43208626 43628550 43218475
               41928463 40908488 40528575 40678738 41578905 42158927
               42158850 41608730 

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Page last modified: July 19, 2015
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