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Mesoscale Discussion 74
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   Mesoscale Discussion 0074
   NWS Storm Prediction Center Norman OK
   0628 AM CST Thu Jan 19 2017

   Areas affected...South-central Louisiana to southwest Mississippi

   Concerning...Severe potential...Watch unlikely 

   Valid 191228Z - 191430Z

   Probability of Watch Issuance...20 percent

   SUMMARY...The threat for a couple occurrences of damaging wind and a
   brief tornado exists through this morning from south-central
   Louisiana into southwest Mississippi.  The overall severe-weather
   threat does not appear sufficient for a WW at this time.

   DISCUSSION...Trends in lightning data and radar imagery during the
   overnight to early this morning showed an increase in thunderstorm
   coverage along and east of a surface boundary that extended from
   southwest to northeast LA to extreme eastern AR.  11z mesoanalysis
   showed the primary synoptic low located in northwest LA with a
   sub-synoptic low in east-central LA (southeast of ESF).  A warm
   front is draped across southern MS to southwest AL marking the
   northward extension of greater moisture return (surface dew points
   in the upper 60s).  Trends during the last few hours with 850-mb
   winds across east and southeast LA to southern MS showed flow
   backing to southerly, while southwesterly 500-mb winds extending
   from the TX coastal Plains to LA strengthened.  These kinematic
   trends will continue this morning as heights fall across the
   discussion area with the approach of a shortwave trough across the
   southern Plains.

   The most recent stronger storms having periodic low-level storm
   rotation were located east of the aforementioned south-southwest to
   north-northeast oriented surface boundary.  Storms located on the
   eastern periphery of the thunderstorm clusters will continue to have
   unimpeded access to backed southeasterly surface winds, enhancing
   low-level shear.  Effective bulk shear of 30-35 kt and further
   strengthening of the low-level jet through this morning across the
   moist warm sector will be supportive of storm organization. 
   However, limited surface heating and marginal buoyancy should tend
   to limit the coverage of strong to severe storms.

   ..Peters/Grams.. 01/19/2017


   LAT...LON   30019200 31419194 32389138 32489020 32068966 29929096
               29639130 29629197 30019200 

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