SPC MESOSCALE DISCUSSION 1812 FOR WRN NEB/NE CO
   CONCERNING...SEVERE THUNDERSTORM WATCH 637...638...
   
   VALID 262010Z - 262200Z
   
   INSTABILITY AXIS EXTENDS FROM WESTERN CHERRY COUNTY NEB CELL
   SOUTHWARD INTO NORTHEAST COLORADO...EAST OF AKRON.  THIS IS ON
   THERMAL GRADIENT EAST OF LOW-LEVEL THERMAL RIDGE/SURFACE TROUGH
   AXIS...WHERE MID-LEVEL LAPSE RATES ARE STEEPEST...AND CONTRIBUTING
   TO SURFACE-BASED CAPE IN EXCESS OF 2000 J/KG.  ACTIVITY NEXT COUPLE
   OF HOURS WILL CONTINUE TO DEVELOP SOUTHWARD ALONG THIS AXIS ACROSS
   WESTERN NEBRASKA...WHILE SOUTHWEST NEBRASKA CONVECTIVE CLUSTER
   PERSISTS...DEVELOPS NORTHWARD.  MERGER OF TWO CONVECTIVE SYSTEMS
   APPEARS POSSIBLE SOUTHEAST OF ALLIANCE BY THE 26/23Z-27/00Z TIME
   FRAME...WHERE EVOLUTION OF LARGER CONVECTIVE SYSTEM WILL CONTINUE
   INTO THE EVENING HOURS...ALONG/WEST OF SOUTHERLY LOW-LEVEL JET AXIS
   ...WHICH WILL INCREASE TO AROUND 40 KT EARLY THIS EVENING.
   
   LOW-LEVEL CONVERGENCE WILL REMAIN FOCUSED NEAR INTERSECTION OF
   CONVECTIVELY ENHANCED BOUNDARY AND LEE SURFACE TROUGH...NORTH/
   NORTHWEST OF GOODLAND KANSAS INTO THE EVENING HOURS.  THIS WILL
   HELP MAINTAIN QUASI-STATIONARY CLUSTER OF THUNDERSTORMS BENEATH
   INCREASINGLY DIFLUENT/DIVERGENT UPPER FLOW REGIME...AND EXCESSIVE
   RAIN TOTALS WILL BECOME INCREASING THREAT.
   
   ..KERR.. 08/26/02