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Mesoscale Discussion 313
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   Mesoscale Discussion 0313
   NWS Storm Prediction Center Norman OK
   1136 AM CDT Wed May 02 2018

   Areas affected...Eastern TX/OK Panhandles western OK to parts of
   southwest and south-central KS

   Concerning...Severe potential...Tornado Watch likely 

   Valid 021636Z - 021900Z

   Probability of Watch Issuance...95 percent

   SUMMARY...Development of additional thunderstorms is expected
   between 17-19Z across portions of the Texas Panhandle into the
   eastern Oklahoma Panhandle into southwest and south-central Kansas. 
   Severe storms will be likely by early afternoon, with all severe
   hazards possible, including very large hail and a tornado threat.

   DISCUSSION...Trends in morning surface analyses and visible
   satellite imagery showed a quasistationary boundary extending from
   extreme southeast NE to southwest KS into the OK Panhandle (east of
   KGUY) to far northern TX Panhandle.  In KS this boundary was
   analyzed at 15Z to the south of KCNK and south of KGBD.  Although
   surface heating, given breaks in high-level clouds, is resulting in
   mixing, persistent southerly low-level winds are compensating to
   maintain surface dew points in the middle-upper 60s from the eastern
   TX Panhandle into western and central OK to southern and eastern KS.
   Moisture return has also spread farther westward this morning into
   more of the TX Panhandle.  This moisture combined with diabatic
   heating will further weaken inhibition, resulting very strong
   instability (MUCAPE of 2500-3500 J/kg) this afternoon. 

   Recent lightning data, satellite and radar imagery showed a storm
   had developed near the intersection of the quasistationary boundary
   and dry line in Hansford County TX (extreme northern TX Panhandle).

   A 70-75 kt southwesterly 500-mb jet accompanying a shortwave trough
   will move through the southern High Plains early this afternoon and
   proceed downstream into western OK to central KS by late afternoon. 
   Forcing for ascent attendant to this trough and exit region of the
   500-mb jet are expected to reach western portions of the discussion
   area between 17-19Z supporting additional storm development into the
   afternoon.  This scenario is suggested by the last several runs of
   the operational HRRR and the 12Z HREF.  These initial storms will
   continue to form from the northern TX Panhandle to part of southwest
   and adjacent south-central KS where low-level convergence is the
   strongest, given strengthening low-level winds into the
   quasistationary boundary.  Storms will also develop equatorward
   along and east of the dryline, as it mixes eastward this afternoon
   into the eastern TX/OK Panhandles, and into western OK.  The
   available MUCAPE and increasing effective bulk shear will be
   favorable for supercells producing tornadoes, very large hail, and
   damaging winds.  Storms that develop along the dryline and into
   western OK will have a greater likelihood to be discrete, given
   shear vectors crossing the initiation boundary.  Shear vectors in
   vicinity of the boundary in KS may tend to be more parallel
   resulting in bows with embedded supercells.

   ..Peters/Grams.. 05/02/2018

   ...Please see for graphic product...


   LAT...LON   34580139 35800143 37050058 38399882 39269745 38879669
               38139647 37029768 35289889 34409920 34380083 34580139 

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