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Mesoscale Discussion 291
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   MESOSCALE DISCUSSION 0291
   NWS STORM PREDICTION CENTER NORMAN OK
   0248 PM CDT MON APR 13 2015

   AREAS AFFECTED...PORTIONS W-CENTRAL TX.

   CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY 

   VALID 131948Z - 132145Z

   PROBABILITY OF WATCH ISSUANCE...5 PERCENT

   SUMMARY...THUNDERSTORMS ARE EXPECTED TO CONTINUE FORMING ON BOTH
   SIDES OF COLD FRONT OVER THIS REGION...MORE COMMONLY ALONG AND
   BEHIND THAN AHEAD OF IT.  A BRIEF/SMALL/NON-MESOCYCLONE TORNADO
   CANNOT BE RULED OUT WITH ANY SFC-BASED CONVECTION CLOSE TO THAT
   BOUNDARY...AND ISOLATED TO WIDELY SCATTERED AND MRGLLY SVR HAIL ALSO
   IS POSSIBLE.  WW IS NOT ANTICIPATED ATTM FOR THIS AREA...THOUGH ONE
   MAY BE NEEDED FARTHER E AND LATER THIS AFTN.

   DISCUSSION...SFC MESOANALYSIS REVEALS TWO PRIMARY LOWS - ONE IN NE
   TX NEAR SLR AND ANOTHER ON WRN FRINGE OF DISCUSSION AREA NEAR BPG. 
   COLD FRONT CONNECTS THESE TWO LOWS AND WAS DRAWN AT 19Z FROM ERN LOW
   TO HILL...COLEMAN AND NRN STERLING COUNTIES.  FRONTAL SEGMENT
   BETWEEN BPG-BWD WAS MOVING SLOWLY SWD -- ABOUT 10 KT.  COLD FRONT
   ALSO EXTENDED THROUGH WRN LOW AND WAS SURGING SWD ACROSS PERMIAN
   BASIN REGION.  PAC COLD FRONT AND DRYLINE WERE DRAWN BETWEEN SFC LOW
   AND NRN MEX...LATTER EXTENDING SWD TO SERRANIAS DEL BURRO AND FORMER
   INTO BIG BEND REGION.  FRONT ITSELF...E OF WRN LOW...IS PRIMARY
   LOW-LEVEL INFLUENCE ON THIS DISCUSSION AREA. 

   NARROW CORRIDOR OF EFFECTIVELY SFC-BASED INSTABILITY APPEARS TO
   EXTEND ALONG AND BEHIND SFC FRONT...IN CONJUNCTION WITH WELL-DEFINED
   MOIST AXIS CHARACTERIZED BY LOW-60S F SFC DEW POINTS.  FARTHER
   N...CAA AND PRECIP EACH STABILIZE AIR MASS SUBSTANTIALLY...AND THAT
   ZONE OF STABILIZATION WILL SHIFT S IN STEP WITH PROGRESS OF COLD
   FRONT ALONG ITS SRN EDGE...ULTIMATELY UNDERCUTTING SFC-BASED
   CONVECTION NEAR FRONT.  RELATIVE CONCENTRATION OF LOW-LEVEL
   VORTICITY ALONG THIS BOUNDARY WILL BE JUXTAPOSED WITH 75-150 J/KG OF
   SFC-3 KM CAPE.  BY ITSELF...THIS WOULD SIGNAL SOME POTENTIAL FOR
   NON-SUPERCELL TORNADOES...THOUGH ACTUAL THREAT IS STRONGLY LIMITED
   BY PROGRESSIVE NATURE OF BOUNDARY.  ALSO...WHILE HAIL IS
   POSSIBLE...FCST SOUNDINGS AND MODIFIED 12Z MAF RAOB INDICATE WEAK
   LAPSE RATES ALOFT THAT WILL TEMPER BOTH DEEP BUOYANCY AND RISK FOR
   MORE THAN MRGL-SVR HAIL.  A STG OR DAMAGING GUST ALSO MAY OCCUR
   ALONG AND S OF FRONT WHERE DOWNDRAFTS PENETRATE BEST-MIXED BOUNDARY
   LAYER.

   ..EDWARDS/GRAMS.. 04/13/2015


   ATTN...WFO...FWD...SJT...MAF...

   LAT...LON   31570080 32420118 32189899 31439890 31570080 

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Page last modified: April 13, 2015
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