MESOSCALE DISCUSSION 0706
   NWS STORM PREDICTION CENTER NORMAN OK
   0558 PM CDT SAT MAY 15 2004
   
   AREAS AFFECTED...CENTRAL PORTIONS ND/SD
   
   CONCERNING...SEVERE THUNDERSTORM POTENTIAL 
   
   VALID 152258Z - 160030Z
   
   ISOLATED HAIL/DAMAGING WINDS WILL BE POSSIBLE WITH ANY DISCRETE
   STORMS THAT DEVELOP DURING THE NEXT 2-3 HOURS FROM CENTRAL ND SWD
   INTO CENTRAL SD.
   
   22Z SURFACE ANALYSIS/VIS IMAGERY SHOWED A TROUGH EXTENDING GENERALLY
   N-S ACROSS THE DAKOTAS FROM 60 NW DVL TO 20 NE VTN...AS A COLD FRONT
   ADVANCES ESEWD ACROSS NORTH CENTRAL ND AND NWRN SD.  A NARROW AXIS
   OF MARGINAL INSTABILITY EXISTS ALONG THE SURFACE TROUGH WHERE
   SURFACE HEATING AND STEEPER MID-LEVEL LAPSE RATES ARE BEGINNING TO
   SPREAD ACROSS THE REGION WITH THE UPPER TROUGH.  IT APPEARS THAT THE
   DISCRETE STORMS THAT ARE DEVELOPING ALONG THE SURFACE TROUGH ARE
   BEING FED FROM THE WSW AS THEY MOVE ESEWD ATOP A COOLER BOUNDARY
   LAYER WHICH HAS BEEN INHIBITED FROM DESTABILIZATION BY CLOUDS.
   
   DEEP LAYER SHEAR IS MORE THAN SUFFICIENT FOR SUPERCELLS WITH
   ADDITIONAL DEVELOPMENT MOST LIKELY FROM ACROSS PORTIONS OF CENTRAL
   SD AS LARGE SCALE ASCENT WITH THE UPPER TROUGH.  HOWEVER...AS STORMS
   MOVE EWD AWAY FROM THE INSTABILITY SOURCE...THEY SHOULD WEAKEN. 
   THIS WILL RESULT IN A SMALL SPATIAL/TEMPORAL WINDOW FOR SEVERE
   POTENTIAL /THROUGH 01-02Z ACROSS SD/...PRIOR TO THE COLD FRONT
   PASSAGE...AS HAS BEEN OBSERVED PER REGIONAL RADARS ACROSS ND.
   
   ..PETERS.. 05/15/2004
   
   
   ATTN...WFO...FGF...FSD...ABR...BIS...UNR...
   
   47770001 47779873 46329809 45769809 44459839 43449900
   43530018 46090040