MESOSCALE DISCUSSION 2084
   NWS STORM PREDICTION CENTER NORMAN OK
   1245 PM CST SUN DEC 27 2015

   AREAS AFFECTED...EAST TX...SOUTHWEST AR AND NORTHWEST LA

   CONCERNING...TORNADO WATCH 571...

   VALID 271845Z - 272045Z

   THE SEVERE WEATHER THREAT FOR TORNADO WATCH 571 CONTINUES.

   SUMMARY...TORNADO THREAT CONTINUES ACROSS WW 571...WITH THIS WATCH
   EXPANDED IN AREA TO INCLUDE A FEW MORE COUNTIES IN SOUTHWEST AR THAT
   REMAIN IN THE WARM SECTOR.  NEW STORM DEVELOPMENT IS EXPECTED TO
   CONTINUE TO OCCUR ALONG THE COLD FRONT AND WITHIN PRE-FRONTAL
   CONFLUENCE ZONES ACROSS THE WARM SECTOR.

   AS THE COLD FRONT MOVES INTO THE WESTERN PART OF WW 571 AND THE
   NEAR-SURFACE BOUNDARY LAYER STABILIZES...STORMS SHOULD BECOME LESS
   CONDUCIVE TO PRODUCE TORNADOES...THOUGH HAIL AND/OR STRONG WIND
   GUSTS WILL BE POSSIBLE.

   DISCUSSION...AT 18Z...GREATER SURFACE PRESSURE FALLS WERE NOTED IN
   SOUTHEAST TX WITH AN AREA OF LOW PRESSURE BECOMING BETTER DEFINED
   NEAR UTS.  THIS LOW IS FORMING ALONG A SLOW EASTWARD-MOVING COLD
   FRONT THAT EXTENDED FROM EXTREME SOUTHEAST OK THROUGH EAST TX TO
   ALONG OR JUST EAST OF THE SOUTH TX COAST.  THE SURFACE ANALYSIS
   INDICATED THE PORTION OF THE COLD FRONT IN AR IS ORIENTED GENERALLY
   WEST-EAST...EXTENDING FROM EXTREME SOUTHEAST OK TO 10 S HOT TO
   APPROXIMATELY 20 NE PBF...AND THEN NORTHEAST INTO EXTREME SOUTHWEST
   TN /JUST NORTH OF MEMPHIS/.  THE TX PORTION OF THE COLD IS FORECAST
   TO MAINTAIN A SLOW EAST MOVEMENT...WHILE THE W-E ORIENTED BOUNDARY
   IN SOUTHERN AR MAY ADVANCE A LITTLE MORE TO THE SOUTH...BUT SHOULD
   STALL IN THE NORTHERN EXTENT OF WW 571 LATER THIS AFTERNOON.

   VISIBLE SATELLITE IMAGERY SHOWED BREAKS IN THE CLOUDS ACROSS THE
   WARM SECTOR IN EAST TX...LA AND SOUTHERN AR THAT HAVE ALLOWED
   SURFACE TEMPERATURES TO RISE INTO THE UPPER 70S TO AROUND 80 F. 
   THIS COMBINED WITH THE PRESENCE OF A VERY MOIST AIR MASS IS
   RESULTING IN MLCAPE OF 1000-2000 J/KG IN EAST TX AND WRN/SRN
   LA...WHILE OBJECTIVE ANALYSES INDICATED MLCAPE OF 500-1000 J/KG IN
   SOUTHERN AR.  SPECIAL 18Z SOUNDINGS AT SHV/LCH CONFIRMED THE 
   OBJECTIVE THERMODYNAMIC ANALYSIS AND ALSO INDICATED STRONG
   KINEMATICS PERSISTED...WITH SOUTHEASTERLY SURFACE WINDS VEERING AND
   STRENGTHENING IN THE LOWEST 1 KM TO SLY AT 50 KT.  EFFECTIVE BULK
   SHEAR OF 40-50 KT AND SFC-3-KM SRH EXCEEDING 300 M2/S2 REMAINS QUITE
   FAVORABLE FOR SUPERCELLS WITH A TORNADO THREAT.

   ..PETERS.. 12/27/2015


   ATTN...WFO...LZK...LCH...SHV...HGX...FWD...CRP...EWX...

   LAT...LON   29769707 31499618 32889547 33599491 34319415 34209386
               33839339 32289347 31399338 30379372 29879447 29569521
               29229604 28679642 28949759 29769707