SPC MESOSCALE DISCUSSION 1089 FOR SRN MT/NERN WY/SRN ND/NWRN SD
CONCERNING...SEVERE THUNDERSTORM POTENTIAL...

VALID 091957Z - 092200Z

RAPID THUNDERSTORM DEVELOPMENT IS POSSIBLE OVER PORTIONS OF SRN MT
AND NERN WY OVER THE NEXT 1-2 HOURS.  SUPERCELLS ARE LIKELY...ALONG
WITH THE POSSIBILITY OF TORNADOES.  WW MAY BE REQUIRED SHORTLY...
REPLACING PARTS OF SVR TSTM WATCH 382. 

MID LEVEL THERMAL RIDGE IS SHIFTING EAST AS UPPER TROUGH AND
ASSOCIATED COOLING MOVE OFF THE NRN ROCKIES INTO THE NRN HIGH
PLAINS.  OVER THE LAST HOUR...CONSIDERABLE AMOUNT OF MID LEVEL
CONVECTION HAS DEVELOPED ALONG THE WRN EDGE OF STRONGER MID LEVEL
WARM ADVECTION ACROSS SERN MT AND NRN WY.  THIS ACTIVITY REPRESENTS
ZONE OF CONCERN AS UPDRAFTS SHIFT EAST OVER BOUNDARY LAYER THAT IS
QUITE UNSTABLE...SFC-BASED CAPE VALUES ON THE ORDER OF 3000 J/KG. 
VERTICAL SHEAR PROFILES FAVOR ROTATING UPDRAFTS AND SUPERCELLS ARE
LIKELY AS ACTIVITY ROOTS INTO HIGHER BOUNDARY LAYER MOISTURE.  WITH
TIME THUNDERSTORMS SHOULD ORGANIZE AND PROPAGATE EAST INTO PORTIONS
OF SWRN ND...OR MORE LIKELY NWRN SD.

..DARROW.. 06/09/01