SPC AC 211139
   
   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0639 AM CDT TUE MAY 21 2013
   
   VALID 211300Z - 221200Z
   
   ...THERE IS A MDT RISK OF SVR TSTMS OVER PARTS OF CENTRAL AND EAST
   TX...SOUTHEAST OK...NORTHWEST LA...AND WESTERN AR...
   
   ...THERE IS A SLGT RISK OF SVR TSTMS FROM THE SOUTHERN PLAINS INTO
   THE MID MS VALLEY AND GREAT LAKES STATES...
   
   ...TX/OK/AR/LA...
   MORNING WATER VAPOR IMAGERY SHOWS A WELL-DEFINED UPPER TROUGH OVER
   THE NM/TX BORDER.  THIS FEATURE IS FORECAST TO TRACK EASTWARD INTO
   THE SOUTHERN PLAINS TODAY...SETTING THE STAGE FOR ANOTHER ACTIVE DAY
   OF SEVERE THUNDERSTORMS.
   
   SCATTERED STRONG THUNDERSTORMS ARE ONGOING THIS MORNING ACROSS
   SOUTHERN OK...IN A REGION OF LOW LEVEL WARM ADVECTION AND AHEAD OF A
   SURFACE COLD FRONT.  THESE STORMS APPEAR LIKELY TO INCREASE IN
   COVERAGE THROUGH THE MORNING...SPREADING SOUTHEASTWARD INTO NORTH TX
   AND WESTERN AR.  AMPLE LOW LEVEL MOISTURE AND MODERATE CAPE VALUES
   WILL POSE A RISK OF LARGE HAIL AND LOCALLY DAMAGING WINDS.  
   
   BY EARLY AFTERNOON...STRONG HEATING SOUTH OF THE STORMS WILL PROMOTE
   FURTHER INTENSIFICATION ACROSS MUCH OF NORTH CENTRAL AND NORTHEAST
   TX.  STEEP MID LEVEL LAPSE RATES AND DEWPOINTS NEAR 70F WILL YIELD
   MLCAPE VALUES OF 2000+ J/KG.  AS THE UPPER TROUGH
   APPROACHES...STRENGTHENING VERTICAL SHEAR SUGGESTS A RISK OF
   DISCRETE SUPERCELLS CAPABLE OF VERY LARGE HAIL AND TORNADOES.  
   
   THE ACTIVITY IS FORECAST TO CONGEAL INTO LINES/CLUSTERS OF STORMS BY
   EARLY EVENING SPREADING RAPIDLY EASTWARD INTO AR/LA.  THESE STORMS
   WILL LIKELY HAVE AN ENHANCED RISK OF WIDESPREAD DAMAGING WINDS.
   
   ...MO/IL NORTHWARD INTO LOWER MI...
   MULTIPLE BANDS OF THUNDERSTORMS HAVE AFFECTED THE MID MS VALLEY
   OVERNIGHT.  THESE STORMS HAVE WEAKENED INSTABILITY AND ARE PROVIDING
   UNCERTAINTY REGARDING THE COVERAGE/INTENSITY OF THUNDERSTORMS LATER
   TODAY.  HAVE MAINTAINED THE SLIGHT RISK AREA...BUT HAVE GENERALLY
   DECREASED PROBABILITIES IN THESE REGIONS.  THE AREA THAT APPEARS
   MOST LIKELY TO SEE ISOLATED SEVERE STORMS LATER TODAY WOULD BE
   ACROSS LOWER MI AS A SHORTWAVE TROUGH NOW OVER MO/IL ROTATES
   NORTHEASTWARD.
   
   ..HART/LEITMAN.. 05/21/2013
   
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   NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1630Z