MESOSCALE DISCUSSION 0478
   NWS STORM PREDICTION CENTER NORMAN OK
   0250 PM CDT MON APR 15 2013
   
   AREAS AFFECTED...PARTS OF NORTH CENTRAL TX INTO ERN OK AND NWRN AR
   
   CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE 
   
   VALID 151950Z - 152115Z
   
   PROBABILITY OF WATCH ISSUANCE...60 PERCENT
   
   SUMMARY...TSTM DEVELOPMENT IS EXPECTED THIS AFTERNOON ACROSS PART OF
   NORTH CENTRAL TX INTO SRN AND ERN OK.  SOME OF THESE STORMS WILL BE
   CAPABLE OF BECOMING SEVERE WITH ALL SEVERE THREATS POSSIBLE. WHILE
   TIMING OF WATCH ISSUANCE REMAINS UNCERTAIN...A WW MAY BE NEEDED
   WITHIN THE NEXT COUPLE OF HOURS.
   
   DISCUSSION...EARLY-MID AFTERNOON SURFACE ANALYSES SHOWED A NEARLY
   STATIONARY FRONT EXTENDING SWWD FROM NERN OK TO NEAR KMKO...AND 25
   NNW KADM WHERE IT INTERSECTED A DRY LINE. THE DRY LINE THEN EXTENDED
   SWWD INTO NRN TX TO THE TX BIG COUNTRY WHERE THERE WAS A SECOND
   INFLECTION WITH THE DRY LINE EXTENDING MORE SWD ACROSS THE EDWARDS
   PLATEAU. LOW LEVEL MOISTENING ACROSS THE WARM SECTOR AND STRONG
   SURFACE HEATING FROM THE TX BIG COUNTRY INTO SOUTH CENTRAL OK IS
   AIDING IN A MODERATELY UNSTABLE AIR MASS /MLCAPE 1500-2000 J PER
   KG/. 
   
   VISIBLE SATELLITE IMAGERY SHOWED CU INCREASING IN COVERAGE AND DEPTH
   INVOF THE FRONT/DRY LINE INTERSECTION IN SRN OK AND SWWD/SWD ALONG
   THE DRY LINE INTO THE TX BIG COUNTRY. FORCING ALOFT MAY INCREASE
   SOME AS AN APPARENT MIDLEVEL WIND MAX/JET MOVES FROM FAR W TX INTO
   NRN TX LATE THIS AFTERNOON. THIS COMBINED WITH FURTHER SURFACE
   HEATING AND INCREASING LOW LEVEL CONVERGENCE ALONG AFOREMENTIONED
   BOUNDARIES SUGGESTS SCATTERED TSTM DEVELOPMENT IS PROBABLE. 
   EFFECTIVE BULK SHEAR OF 35-45 KT IS SUFFICIENT FOR STORM
   ORGANIZATION WITH STEEP LAPSE RATES SUPPORTING HAIL AND STRONG
   DAMAGING WINDS.  LOW LEVEL VERTICALLY VEERING WINDS IN NRN TX WITH
   0-3 KM SRH AROUND 200 M2/S2 SUGGESTS A TORNADO THREAT CANNOT BE
   RULED OUT.
   
   ..PETERS/KERR.. 04/15/2013
   
   
   ATTN...WFO...LZK...SGF...SHV...TSA...FWD...OUN...
   
   LAT...LON   32679846 34159759 35389661 36619489 36459337 35289384
               33139569 32379684 32399773 32679846