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Mesoscale Discussion 901
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   Mesoscale Discussion 0901
   NWS Storm Prediction Center Norman OK
   0134 PM CDT Sun May 28 2017

   Areas affected...Central Texas

   Concerning...Severe potential...Watch likely 

   Valid 281834Z - 281930Z

   Probability of Watch Issuance...80 percent

   SUMMARY...A severe weather watch seems probable at some point late
   this afternoon and evening, perhaps as early as 20-21Z.

   DISCUSSION...Objective analysis indicates that insolation within a
   boundary layer characterized by high moisture content (lower/mid 70s
   F surface dew points) is contributing to strong/extreme CAPE on the
   order of 4000+ J/kg across much of the region, including the
   Interstate 35 corridor between San Antonio and Waco.  Mid-level
   inhibition beneath warm elevated mixed layer air does still appear
   considerable, particularly given weak, or at least unclear,
   mid/upper forcing for ascent.  An area of enhanced ascent
   contributing to deepening mid-level based convection near the
   Interstate 20 corridor, west of the Dallas/Fort Worth metroplex, may
   remain displaced to the north of an area of sustained enhanced
   low-level convergence near the Waco area.  This is near the
   intersection of a surface front that extends southwestward into the
   Rio Grande Valley, to the west of Del Rio, and the western flank of
   composite outflow from extensive overnight convection, now advancing
   into the north central Gulf Coast.

   However, the latest Rapid Refresh suggests that additional surface
   heating, coupled with subtle mid-level height falls on the southern
   fringe of the westerlies, may be sufficient to support the
   initiation of thunderstorms as early as 20-21Z.  Once this does
   occur, intensification likely will be very rapid, and deep layer
   shear appears sufficient for the evolution of supercell structures
   with large hail  and perhaps an isolated tornado, in addition to
   strong downbursts accompanied by potentially damaging surface gusts.

   ..Kerr/Hart.. 05/28/2017

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

   ATTN...WFO...HGX...FWD...EWX...SJT...

   LAT...LON   30359938 31149852 31689787 31949702 31599588 30929570
               30419690 29639779 29409830 29329912 30359938 

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Page last modified: May 28, 2017
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