MESOSCALE DISCUSSION 0708
   NWS STORM PREDICTION CENTER NORMAN OK
   0156 AM CDT TUE MAY 10 2011
   
   AREAS AFFECTED...NWRN SD AND PARTS OF SRN/CENTRAL AND ERN ND
   
   CONCERNING...SEVERE THUNDERSTORM WATCH 267...
   
   VALID 100656Z - 100830Z
   
   THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH 267
   CONTINUES.
   
   GIVEN CURRENT CONVECTIVE TRENDS ACROSS NWRN SD SHOWING A LOWER
   NUMBER OF STRONGER STORMS...WW 267 WILL BE ALLOWED TO EXPIRE AS
   SCHEDULED AT 08Z.  UNTIL THEN...AND ALSO THROUGH THE OVERNIGHT
   ACROSS SRN/CENTRAL AND ERN ND...ISOLATED SEVERE STORMS REMAIN
   POSSIBLE WITH HAIL BEING THE PRIMARY THREAT FROM THE ELEVATED
   ACTIVITY. 
   
   RECENT WATER VAPOR IMAGERY SHOWED A SHORTWAVE TROUGH LOCATED OVER
   ERN WY...WITH THIS FEATURE EXPECTED TO MOVE INTO THE WRN DAKOTAS BY
   12Z RESULTING IN THE STRONGEST FORCING ALOFT TO AFFECT THE WRN
   DAKOTAS.  ALTHOUGH EFFECTIVE BULK SHEAR REMAINS STRONG /AROUND 50
   KT/ ACROSS THE VALID PART OF WW 267 TO SUPPORT ORGANIZED
   STORMS...WEAKENING AVAILABLE INSTABILITY IN THIS AREA SUGGESTS THE
   OBSERVED DECREASE IN STRONGER UPDRAFTS SHOULD PERSIST.
   
   MEANWHILE...A 50 KT SSELY LLJ EXTENDS ACROSS ERN SD WITH STRONG LOW
   LEVEL WAA EXPECTED TO DEVELOP NWD INTO ND OVERNIGHT/EARLY THIS
   MORNING AS THE ABOVE MENTIONED TROUGH AND EWD EXTENDING WARM FRONT
   SPREAD NWD.  THE LLJ WILL MAINTAIN A FEED OF MODERATE INSTABILITY
   INTO CENTRAL/ERN ND.  THIS COMBINED WITH THE LOW LEVEL WAA WILL
   SUPPORT TSTMS DEVELOPING/MOVING NWD...BUT GIVEN STRONGER FORCING
   ALOFT REMAINING WEST OVER THE WRN DAKOTAS...THE OVERALL COVERAGE OF
   STRONGER STORMS IS NOT EXPECTED TO BE SUFFICIENT TO WARRANT A NEW
   WATCH.
   
   ..PETERS.. 05/10/2011
   
   
   ATTN...WFO...FGF...ABR...BIS...UNR...
   
   LAT...LON   44290097 44360256 44940367 45930326 47600037 47719841
               47599706 46269641 45879640 46069758 46369902 45860011
               44690047 44440040 44290097