MESOSCALE DISCUSSION 0781
   NWS STORM PREDICTION CENTER NORMAN OK
   0249 PM CDT SUN MAY 13 2007
   
   AREAS AFFECTED...SWRN AND S CNTRL THROUGH ERN MT AND EXTREME NRN WY
   
   CONCERNING...SEVERE POTENTIAL...WATCH LIKELY 
   
   VALID 131949Z - 132045Z
   
   STORMS ARE EXPECTED TO DEVELOP OVER THE HIGHER TERRAIN OF SWRN MT
   AND NWRN WY AND INTENSIFY AS THEY MOVE NEWD INTO S CNTRL AND ERN MT.
   ISOLATED LARGE HAIL AND DAMAGING WIND WILL BE THE MAIN THREATS. WW
   WILL LIKELY BE NEEDED ONCE SURFACE BASED INITIATION APPEARS
   IMMINENT.
   
   A COLD FRONT EXTENDS FROM NERN MT NEAR GLASGOW SWWD INTO ERN ID. AN
   OUTFLOW BOUNDARY WAS SETTLING SLOWLY SWD JUST N OF BILLINGS. NELY
   LOW LEVEL FLOW WITHIN PRE-FRONTAL WARM SECTOR IS HELPING TO MAINTAIN
   SURFACE DEWPOINTS IN THE LOW TO MID 50S ACROSS SRN AND ERN MT
   BENEATH 7.5-8 C/KM 700-500 MB LAPSE RATES. THIS ALONG WITH STRONG
   SURFACE HEATING IS RESULTING IN DESTABILIZATION WITH MLCAPE FROM
   1000 TO 1500 J/KG IN THIS REGION. VISIBLE IMAGERY SHOWS CUMULUS
   DEVELOPING OVER THE HIGHER TERRAIN OF SWRN MT AND NERN ID. THE
   CONVECTIVE POTENTIAL SHOULD CONTINUE TO INCREASE AS THE CAP WEAKENS
   AND LARGE SCALE ASCENT ASSOCIATED WITH EWD ADVANCING SHORTWAVE
   TROUGH SPREADS EWD THROUGH THIS AREA. STORMS WILL LIKELY DEVELOP
   INITIALLY OVER THE HIGHER TERRAIN THEN SPREAD NEWD THROUGH THE WARM
   SECTOR. A 40 TO 50 KT MID LEVEL JET ALONG ERN PERIPHERY OF THE
   SHORTWAVE TROUGH ABOVE WEAK ELY BOUNDARY LAYER FLOW IS RESULTING IN
   FAVORABLE VERTICAL SHEAR FOR INITIAL STORMS TO DEVELOP SUPERCELL
   STRUCTURES. PRIMARY THREATS WILL BE ISOLATED DAMAGING WIND AND LARGE
   HAIL. HOWEVER...AN ISOLATED TORNADO OR TWO MAY ALSO BE
   POSSIBLE...MAINLY WITH ANY STORMS ADVANCING NEWD AND INTERACTING
   WITH THE OUTFLOW BOUNDARY.
   
   ..DIAL.. 05/13/2007
   
   
   ATTN...WFO...BYZ...GGW...RIW...TFX...PIH...
   
   46370500 45000609 44730997 44631114 44901223 45861156
   47130811 47960600 47430507