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Mesoscale Discussion 1442
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   Mesoscale Discussion 1442
   NWS Storm Prediction Center Norman OK
   1038 AM CDT Fri Aug 04 2017

   Areas affected...Much of the upper Ohio Valley

   Concerning...Severe potential...Watch possible 

   Valid 041538Z - 041745Z

   Probability of Watch Issuance...40 percent

   SUMMARY...Severe hail/wind risk with increasing thunderstorm
   development may remain somewhat localized and/or sparse in coverage
   through early to mid afternoon.  However, potential does exist for a
   slow increase in coverage and organization which could be
   accompanied by a more substantive risk for damaging wind gusts later
   this afternoon.  Trends will continue to be monitored for the
   possibility of a watch.

   DISCUSSION...Weak to moderate pre-cold frontal destabilization is
   now underway across much of the upper Ohio Valley, primarily as
   insolation contributes to warming of a seasonably moist boundary
   layer.  Latest objective analysis suggests that inhibition is
   already becoming increasingly negligible, particularly within a
   corridor ahead of the front, from parts of north central Kentucky
   through the Lake Erie area.  Aided by large-scale ascent ahead of a
   significant short wave trough now pivoting eastward toward the lower
   Great Lakes/upper Ohio Valley region, a general increase in
   thunderstorm activity appears likely through 17-20Z.

   Further daytime heating may yield CAPE as high as 1500-2000 J/kg,
   supportive of vigorous updrafts.  However, warm sector southwesterly
   deep layer mean flow, even with some strengthening, appears likely
   to remain on the order of 30-35 kt.  And models indicate that the
   mid-level cold core of the approaching system will lag to the west. 
   Still, weak cooling aloft may be enough to support some risk for
   marginally severe hail in initial stronger pulsing activity. 
   Vertical shear and instability may become marginally sufficient to
   support a gradual increase in convective organization, which may
   eventually be accompanied by an increasing risk for potentially
   damaging wind gusts.  This probably will take some time through,
   with any severe hail/wind risk expected to initially remain fairly
   sparse in coverage.

   ..Kerr/Goss.. 08/04/2017

   ...Please see for graphic product...


   LAT...LON   41348239 42558078 43027834 41277821 38218133 37858388
               39418369 41348239 

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