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Mesoscale Discussion 77
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   Mesoscale Discussion 0077
   NWS Storm Prediction Center Norman OK
   1111 AM CST Tue Feb 20 2018

   Areas affected...Northwest TX...North-Central TX...Far South-Central
   OK

   Concerning...Severe potential...Watch unlikely 

   Valid 201711Z - 201845Z

   Probability of Watch Issuance...20 percent

   SUMMARY...Isolated small hail and damaging wind gusts are possible
   across portions of northwest TX, north-central TX, and far
   south-central OK over the next few hours.

   DISCUSSION...A line of thunderstorms has developed along a dryline
   extending southwestward from just west of SPS to SWW. Atmospheric
   profiles are moist and largely void of steep lapse rates but warm
   and moist conditions just ahead of the dryline (i.e. temperatures in
   the upper 60s/lows and dewpoints in the mid 60s) still support
   modest instability. Latest mesoanalysis estimates MLCAPE around 500
   to 800 J/kg. Kinematics are a bit more favorable for a few stronger
   storms with vertical veering wind profiles shown on regional VADs
   sampling 20-35 kt of 0-1 km shear and around 40 kt of 0-6 km shear.
   Given these wind field, some updraft rotation is possible with the
   more persistent updraft.

   Marginal thermodynamics and favorable kinematics will likely keep
   strong updrafts predominantly short-lived. Additionally, storm
   persistence will be limited by the southward progressing cold front
   currently intersecting the dryline just northwest of SPS. Some
   brief/localized enhancement of updrafts is possible as frontal
   circulations augment lift, but northeastward storm motions will then
   result in an undercutting of updrafts. Overall expectation is for
   isolated small hail and occasional damaging wind gust across the
   region for the next few hours.

   ..Mosier/Weiss.. 02/20/2018

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

   ATTN...WFO...FWD...OUN...SJT...

   LAT...LON   32730008 33939892 34339809 34379709 33379713 32279895
               32109997 32730008 

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Page last modified: February 20, 2018
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