MESOSCALE DISCUSSION 1618
   NWS STORM PREDICTION CENTER NORMAN OK
   0733 PM CDT THU JUL 14 2011
   
   AREAS AFFECTED...ERN MT
   
   CONCERNING...SEVERE THUNDERSTORM WATCH 642...
   
   VALID 150033Z - 150130Z
   
   THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH 642
   CONTINUES.
   
   LOCAL WFO AREAL EXTENSION OF WW 642 IS LIKELY...ESPECIALLY FOR
   CUSTER AND PRAIRIE COUNTIES AS A LINE OF STRONG-SEVERE STORMS
   ADVANCES ENEWD.  A NEW WW IS BEING CONSIDERED FOR ERN MT AND
   ADJACENT WEST CENTRAL/NWRN ND BY 03Z.
   
   AT 0020Z...REGIONAL RADAR IMAGERY SHOWED STORMS OVER SERN MT TRYING
   TO EVOLVE INTO AN MCS...WITH A BOWING TYPE STRUCTURE EXTENDING FROM
   ROSEBUD COUNTY TO NRN BIG HORN COUNTY.  THESE STORMS WERE MOVING
   ENEWD AT 25 KT AND SHOULD REACH WRN CUSTER AND PRAIRIE COUNTIES BY
   02Z.  GIVEN THAT THIS ACTIVITY IS MOVING INTO A MORE UNSTABLE AIR
   MASS AND STRONG EFFECTIVE BULK SHEAR EXISTS FROM CENTRAL/ERN MT INTO
   THE DAKOTAS...THE LIKELIHOOD FOR THE FORMATION OF A FORWARD
   PROPAGATING MCS IS HIGH WITH A GREATER POTENTIAL FOR DAMAGING WINDS.
   
   ..PETERS.. 07/15/2011
   
   
   ATTN...WFO...BIS...UNR...BYZ...GGW...RIW...TFX...
   
   LAT...LON   45000836 45880904 49030823 48970401 48000407 46860483
               45940522 45240622 44560601 44560740 44930802 45000836