SPC MESOSCALE DISCUSSION 1747 FOR NCNTRL/NERN NEB AND CNTRL/SRN SD
   CONCERNING...SEVERE THUNDERSTORM POTENTIAL...
   
   VALID 201850Z - 202200Z
   
   TSTMS WILL LIKELY INCREASE IN INTENSITY AND AREA BEING MONITORED
   FOR A WW ACROSS PORTIONS OF NCNRL/NERN NEB AND CNTRL/SRN SD.
    
   WARM ADVECTION HAS INCREASED RAPIDLY SINCE LATE MORNING AS MIDLEVEL
   SHORTWAVE TROUGH MIGRATES INTO CO AND PRESSURES BEGIN TO FALL
   ACROSS THE CNTRL HIGH PLAINS.  RESULTANT LOW LEVEL FLOW HAS ALSO
   INCREASED...WITH THETA-E ADVECTION STRENGTHENING ACROSS THE NEB/SD
   BORDER.  ELEVATED TSTMS HAVE BEEN INCREASING IN THIS CORRIDOR AND
   SHOULD INTENSIFY AS LARGE SCALE ASCENT ASSOCIATED WITH APPROACHING
   SHORTWAVE MOVES CLOSER TO THE REGION.  STEEP MIDLEVEL LAPSE RATES
   ATOP INCREASING BOUNDARY LAYER MOISTURE IS RESULTING IN RAPID
   DESTABLIZATION AND ELEVATED TSTMS DEVELOPING ATTM MAY PRODUCE LARGE
   HAIL.  HOWEVER...AS WE HEAD THROUGH THE EVENING...TSTMS MAY BECOME
   ROOTED CLOSER TO THE BOUNDARY LAYER NEAR DEVELOPING THERMAL RIDGE
   AXIS NOSING TOWARD NCNTRL/NERN NEB.  NLG PROFILER DEPICTS DEEP
   LAYER SHEAR AROUND 30 KTS...MARGINALLY SUFFICIENT FOR SUPERCELLS. 
   LARGE HAIL...SOME SIGNIFICANT...AND DAMAGING WINDS WILL BE THE
   PRIMARY THREATS.  HOWEVER...IF TSTMS CAN BECOME MORE SURFACE
   BASED...POTENTIAL WILL ALSO EXIST FOR ONE OR TWO TORNADOES OVER
   SCNTRL/SERN SD LATER THIS AFTERNOON AS LOW LEVEL WINDS REMAINED
   BACKED INVOF OF WARM FRONT.
   
   ..RACY.. 08/20/02