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Mesoscale Discussion 32
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   Mesoscale Discussion 0032
   NWS Storm Prediction Center Norman OK
   0113 PM CST Sun Jan 21 2018

   Areas affected...northeast Texas...eastern Oklahoma through western
   Arkansas

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

   Valid 211913Z - 212115Z

   Probability of Watch Issuance...80 percent

   SUMMARY...Thunderstorms are expected to develop by 21Z across
   northeast Texas into eastern Oklahoma and subsequently increase in
   coverage and intensity. Supercells and bowing line segments with
   damaging wind and a few tornadoes should be the primary threats. A
   tornado watch will probably be needed before 21Z.

   DISCUSSION...This afternoon a dryline extends from northeast KS
   through west-central OK to north-central and southwest TX. Pacific
   front will merge with the dryline later this afternoon, and this
   boundary will continue through the southern Plains this evening as a
   surface low consolidates over eastern KS in association with a
   progressive shortwave trough. Modifying continental-polar air with
   low 60s F dewpoints has advected through the warm sector beneath
   modest lapse rates where objective analysis shows a corridor of
   500-800 J/KG MLCAPE from central and northeast TX into southeast OK.
   WV imagery indicates mid-upper level moistening and clouds resulting
   from a band of deeper forcing for ascent moving through eastern OK
   and northeast TX, and scattered showers are already developing over
   northeast TX in association with this process. RAP soundings
   indicate a capping inversion still in place around 750 mb, but
   ascent in the 850-500 mb layer layer will eventually erode the
   inversion, contributing to thunderstorm development by 20-21Z.
   Vertical wind shear will increase as the low-level jet strengthens
   within exit region of the approaching mid-upper jet with large 0-1
   km hodographs and effective-bulk shear exceeding 40 kt. This
   environment should support organized storms including a few discrete
   supercells and bowing line segments as storms intensify later this
   afternoon and evening.

   ..Dial/Grams.. 01/21/2018

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

   ATTN...WFO...LZK...SGF...SHV...TSA...HGX...FWD...OUN...

   LAT...LON   30929680 34139629 36149588 36619432 35819334 33839335
               31329475 30929680 

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Page last modified: January 21, 2018
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