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Mesoscale Discussion 1263
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   Mesoscale Discussion 1263
   NWS Storm Prediction Center Norman OK
   0550 PM CDT Fri Jul 07 2017

   Areas affected...Portions of eastern WI

   Concerning...Severe potential...Watch unlikely 

   Valid 072250Z - 080045Z

   Probability of Watch Issuance...20 percent

   SUMMARY...An isolated large hail and damaging wind threat should
   continue for the next few hours. Watch issuance is unlikely.

   DISCUSSION...Within large-scale upper troughing centered over the
   Great Lakes region, a compact shortwave trough with associated
   mid-level 50+ kt speed maximum is moving southeastward across WI
   late this afternoon. Recent visible satellite and radar imagery show
   a lake breeze boundary extending north-south across eastern WI, and
   several thunderstorms have recently intensified along this boundary
   as large-scale ascent attendant to the shortwave trough overspreads
   this region. While relatively cool surface conditions exist across
   eastern WI behind a surface cold front, there is sufficient cooling
   aloft to support weak instability, with 22Z RAP Mesoanalysis
   estimating up to 500 J/kg of MLCAPE has developed. Strengthening
   northwesterly winds above the boundary layer are supporting around
   40-50 kt of effective bulk shear, and one of the thunderstorms that
   crossed the boundary has exhibited supercell characteristics and
   produced both severe hail (up to 1.5 inches) and tree damage.
   Additional isolated instances of large hail and strong/damaging
   winds will remain possible for the next several hours, with the best
   severe potential likely focused along the lake breeze when
   thunderstorms cross this boundary. This isolated severe threat
   should diminish later this evening with the loss of daytime heating
   and resultant reduction in instability. The limited spatial/temporal
   nature of the threat suggests watch issuance is unlikely.

   ..Gleason/Thompson.. 07/07/2017

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

   ATTN...WFO...GRB...MKX...ARX...

   LAT...LON   44078967 44248924 44418844 44308799 44078762 43708762
               43248786 42788769 42508774 42538883 43598977 44078967 

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