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Mesoscale Discussion 1071
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   Mesoscale Discussion 1071
   NWS Storm Prediction Center Norman OK
   0244 PM CDT Sat Jun 17 2017

   Areas affected...northeast Missouri...southeast Iowa...northern
   Illinois...far southeast Wisconsin...and far northwest Indiana

   Concerning...Severe potential...Watch possible 

   Valid 171944Z - 172145Z

   Probability of Watch Issuance...60 percent

   SUMMARY...Deepening cumulus/showers developing at this time across
   eastern Iowa and northern Illinois are expected to continue evolving
   into isolated thunderstorms.  Accompanying risk for locally damaging
   winds and hail may require watch issuance.

   DISCUSSION...Latest visible satellite loop shows a west-to-east band
   of towering cumulus/small Cb developing from just north of MLI to
   near ORD, and other deepening in the cu field across far northern
   Missouri.  This increase in cumulus development is occurring just
   ahead of the slowly advancing cold front (extending from Lake
   Michigan southwest across southern Wisconsin/eastern Iowa into
   northwest Missouri), where gradual airmass destabilization
   continues.

   Early afternoon RAOBs from DVN -- and particularly from ILX -- show
   a warm troposphere/very weak lapse rates in the 850 to 500 mb layer,
   which will limit CAPE development over the next few hours despite a
   moist boundary layer and continued heating through broken cloud
   cover.  Still, expect continued/gradual increase in the cu field to
   result in isolated thunderstorm development over the next 1-2 hours.

   With ample shear indicated by area VWPs and the aforementioned 18z
   DVN RAOB, owing to mid-level westerly flow currently in the 30 to 40
   kt range, a few of the developing cells may organize, and become
   capable of producing hail and locally gusty/damaging winds.    While
   this development may require WW issuance, greater severe risk is
   expected to evolve later this afternoon/early this evening, as a
   mid-level short-wave trough/jet streak approaches from the west and
   eventually overspreads the area -- yielding an increase in
   large-scale ascent and available shear.

   ..Goss/Weiss.. 06/17/2017

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

   ATTN...WFO...IWX...LOT...ILX...MKX...LSX...DVN...DMX...EAX...

   LAT...LON   40259295 41079283 42269092 42808786 41688666 41258689
               40838809 39859169 40259295 

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Page last modified: June 17, 2017
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