MESOSCALE DISCUSSION 2066
   NWS STORM PREDICTION CENTER NORMAN OK
   1202 PM CST SAT DEC 26 2015

   AREAS AFFECTED...PARTS OF NORTH AND NORTHEAST TX INTO SOUTH AND
   SOUTHEAST OK AND WESTERN AR

   CONCERNING...SEVERE POTENTIAL...TORNADO WATCH LIKELY 

   VALID 261802Z - 261900Z

   PROBABILITY OF WATCH ISSUANCE...80 PERCENT

   SUMMARY...TORNADO WATCH ISSUANCE IS LIKELY ACROSS PARTS OF NORTH TX
   AND SOUTH TO SOUTHEAST OK INTO WESTERN AR.  CONCERN IS INCREASING
   FOR SEVERE WEATHER TO DEVELOP ACROSS THIS REGION THIS AFTERNOON WITH
   ALL SEVERE HAZARDS POSSIBLE INCLUDING A FEW TORNADOES.

   DISCUSSION...TRENDS IN MESONET OBSERVATIONS SHOWED A COLD FRONT HAS
   ADVANCED THROUGH MUCH OF THE WESTERN THIRD OF OK...THE WESTERN HALF
   OF THE TX BIG COUNTRY TO SOUTHWEST TX.  CURRENTLY...THE NORTHERN
   EXTENT FOR SURFACE-BASED STORMS IS LIKELY IN VICINITY OF A WARM
   FRONT THAT EXTENDS FROM JUST SOUTH OF THE OKC METRO /SOUTHERN
   MCCLAIN AND CLEVELAND COUNTIES/ EAST INTO WEST CENTRAL AR...WITH
   SURFACE DEW POINTS IN THE UPPER 60S TO AROUND 70 F SOUTH OF THIS
   BOUNDARY. THE WARM SECTOR ENVIRONMENT ACROSS CENTRAL AND NORTH TX
   INTO PORTIONS OF SOUTHERN AND EASTERN OK AND WESTERN AR IS ALREADY
   CONDUCIVE TO SUPPORT STRONG TO SEVERE STORMS.  THE SPECIAL 18Z FWD
   SOUNDING SAMPLED THIS ENVIRONMENT VERY WELL /MODERATE INSTABILITY
   /MLCAPE EXCEEDING 1500 J PER KG/...EFFECTIVE BULK SHEAR EXCEEDING 50
   KT...AND SFC-3 KM SRH EXCEEDING 300 M2 PER S2/...SUPPORTING THE
   LIKELIHOOD FOR ORGANIZED ROTATING STORMS.  ALTHOUGH STRONGER
   DEEP-LAYER FORCING FOR ASCENT WILL TEND TO REMAIN WEST OF THE WARM
   SECTOR THIS AFTERNOON...EVEN WEAK UPWARD VERTICAL MOTION WITHIN THIS
   ANOMALOUSLY MOIST AND FAVORABLY SHEARED ENVIRONMENT POSES CONCERN
   FOR A TORNADO THREAT.  

   STORMS THAT FORM NEAR OR ALONG THE COLD FRONT SHOULD QUICKLY BECOME
   UNDERCUT BY THIS BOUNDARY AND TEND TO POSE A THREAT FOR PRIMARILY
   HAIL. REFER TO MCD 2065 FOR THIS ELEVATED HAIL THREAT.  THE TORNADO
   THREAT WILL BE ATTENDANT TO NEW UPDRAFTS/STORM DEVELOPMENT FARTHER
   EAST ACROSS THE WARM SECTOR IN NORTH-CENTRAL TX TO SOUTHEAST OK AND
   WESTERN AR.  ACTIVITY IN THIS REGIME WILL TEND TO TRACK PARALLEL TO
   AXES OF LOW-LEVEL CONFLUENCE AHEAD OF THE COLD FRONT...RESULTING IN
   A LONGER GESTATION PERIOD OF THE STRONGER INSTABILITY AND STRONGLY
   SHEARED ENVIRONMENT.

   ..PETERS/MEAD.. 12/26/2015


   ATTN...WFO...LZK...SHV...TSA...FWD...OUN...SJT...

   LAT...LON   35179683 35539547 35599402 35369341 35029325 34359341
               33889401 33419488 32339614 32149666 31699769 31559836
               32029949 32499929 33999803 34539756 35179683