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Mesoscale Discussion 197
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MD 197 graphic

   Mesoscale Discussion 0197
   NWS Storm Prediction Center Norman OK
   0432 AM CST Mon Feb 20 2017

   Areas affected...Deep South Texas

   Concerning...Severe potential...Watch unlikely 

   Valid 201032Z - 201330Z

   Probability of Watch Issuance...20 percent

   SUMMARY...Locally strong wind gusts and/or a brief tornado will be
   possible through 12-14Z across Deep South Texas to portions of the
   middle Texas coast.  Given expected sparse coverage of the overall
   severe-weather threat, a watch is not anticipated into the early
   morning as storms move toward the Texas Gulf coast.

   DISCUSSION...Another forward-propagating MCS has developed across
   Deep South Texas early this morning (since about 08Z per
   radar/satellite trends), with the band of storms extending from Live
   Oak and Jim Wells Counties to the lower Rio Grande River/
   international border in Hidalgo County and into northern Tamaulipas
   Mexico.  Surface analysis showed a convective outflow boundary
   extending northeast from northwest Kenedy County to just inland of
   the middle Texas coast, and then north-northeast to the ongoing MCS
   moving through east Texas.  The environment south of this boundary
   from the middle Texas coast to Deep South Texas remains moderately
   unstable with strong effective bulk shear vectors oriented parallel
   to the surface boundary and the north-south oriented band of storms
   in Deep South Texas.

   These storms appear to be located along the leading edge of forcing
   for ascent and height falls attendant to the large-scale trough
   moving east from the Texas Big Bend region and northern Mexico. 
   This forcing has weakened the cap across Deep South Texas allowing
   for the storms to form within the moderate instability.  Given deep
   meridional flow across the discussion area, propagation of the band
   of storms will remain slow toward the east, while some portions of
   the band/QLCS track to the northeast at 25-30 kt.  Locally strong
   wind gusts will be possible, while effective SRH exceeding 200 m2/s2
   suggest a tornado cannot be ruled out (especially with mesovortices
   within the QLCS).

   ..Peters/Edwards.. 02/20/2017


   LAT...LON   27779771 28939625 28509582 28049661 27599703 26999714
               25949696 25789738 25979818 26519794 27099768 27389768

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