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Mesoscale Discussion 120
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   MESOSCALE DISCUSSION 0120
   NWS STORM PREDICTION CENTER NORMAN OK
   1101 AM CST THU FEB 20 2014

   AREAS AFFECTED...NERN TX...SRN AR...NWRN LA

   CONCERNING...SEVERE POTENTIAL...WATCH LIKELY 

   VALID 201701Z - 201900Z

   PROBABILITY OF WATCH ISSUANCE...80 PERCENT

   SUMMARY...PRE-FRONTAL DEEP CONVECTION HAS JUST COMMENCED ACROSS THE
   ARKLATEX. THIS ACTIVITY WILL INTENSIFY THIS AFTERNOON WITH A
   PREDOMINANT MODE OF SHORT LINE SEGMENTS AND EMBEDDED SUPERCELL
   STRUCTURES LIKELY. ALL SEVERE RISKS APPEAR POSSIBLE...BUT SHOULD
   GENERALLY REMAIN ISOLATED IN COVERAGE THROUGH MID-AFTERNOON.

   DISCUSSION...WITHIN A PRE-FRONTAL CONFLUENCE BAND ALONG THE AXIS OF
   RICHEST LOW-LEVEL MOISTURE ACROSS THE ARKLATEX...LIGHTNING-PRODUCING
   CONVECTION HAS COMMENCED JUST WEST OF SHV IN NERN TX AS A STOUT EML
   NOTED IN 12Z SHV/FWD RAOBS HAS ERODED. ALTHOUGH SURFACE HEATING HAS
   BEEN SLOWED BY ABUNDANT CLOUDINESS WITHIN THE WARM SECTOR...GRADUAL
   DESTABILIZATION WILL CONTINUE AND SHOULD YIELD MODEST BUOYANCY WITH
   MLCAPE INCREASING TO 1000-1500 J/KG. WITH DEEP-LAYER SHEAR GENERALLY
   PARALLELING THIS INITIATION CORRIDOR...ALONG WITH VEER-BACK WIND
   PROFILES SAMPLED IN SHV VWP DATA...CONVECTIVE MODE SHOULD LARGELY
   CONSIST OF SHORT-LINE SEGMENTS. NEVERTHELESS...SUFFICIENT LOW-LEVEL
   SRH WILL EXIST FOR ROTATING UPDRAFTS CAPABLE OF PRODUCING ALL SEVERE
   HAZARDS. 12Z NSSL-WRF APPEARS TO HAVE A REASONABLE SCENARIO WITH
   REGARD TO TIMING OF THIS CONVECTION AND SUGGESTS INTENSITY/COVERAGE
   WILL INCREASE DURING THE AFTERNOON WITH APPROACH OF THE SURFACE COLD
   FRONT.

   ..GRAMS/THOMPSON.. 02/20/2014


   ATTN...WFO...MEG...JAN...LZK...LCH...SHV...HGX...FWD...

   LAT...LON   32489487 33699334 34289264 34659124 34459086 33989078
               32869128 31469313 30819451 30949531 31349580 31839570
               32489487 

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Page last modified: February 20, 2014
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