MESOSCALE DISCUSSION 1020

        MESOSCALE DISCUSSION 1020     NWS STORM PREDICTION CENTER NORMAN OK     0152 PM CDT SAT JUN 02 2012          AREAS AFFECTED...S-CNTRL/ERN MT          CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE           VALID 021852Z - 022045Z          PROBABILITY OF WATCH ISSUANCE...60 PERCENT          SUMMARY...THE THREAT FOR SVR STORMS MAY INCREASE INTO MID     AFTERNOON...FIRST DEVELOPING OVER THE SW MT MOUNTAINS...AND THEN     EXPANDING ENEWD TOWARD THE ADJACENT HIGH PLAINS OF ERN MT.     CONVECTIVE TRENDS WILL CONTINUE TO BE MONITORED FOR THE POSSIBLE     ISSUANCE OF A SVR TSTM WATCH THIS AFTERNOON.          DISCUSSION...MID-LEVEL ASCENT IN ASSOCIATION WITH A SUBTLE SHORTWAVE     IMPULSE CROSSING THE GREAT BASIN AND NRN ROCKIES PER RECENT WATER     VAPOR IMAGERY...IN ADVANCE OF A STRONGER SHORTWAVE TROUGH OVER WA     AND NRN ID...IS CONTRIBUTING TO MARGINAL DESTABILIZATION OVER SWRN     MT AND E-CNTRL ID IN THE WAKE OF EARLIER PRECIPITATION/CONVECTIVE     DEBRIS CLOUDS. AND...WITH MESOSCALE ASCENT OWING TO OROGRAPHIC     INFLUENCES -- IN ADVANCE OF A SFC COLD FRONT DRAPED ACROSS NWRN MT     AND CNTRL ID -- THUNDERSTORMS HAVE BEGUN TO DEVELOP OVER THE SW MT     MOUNTAINS AND ADJACENT SECTIONS OF E-CNTRL ID FROM LEMHI COUNTY ID     INTO BEAVERHEAD COUNTY MT. THIS ACTIVITY WILL CONTINUE MOVING     ENEWD...WHILE ADDITIONAL STORMS DEVELOP FARTHER NE ACROSS THE     MOUNTAINS OF SWRN/S-CNTRL MT WITHIN AN AREA OF ONGOING     CLEARING/DESTABILIZATION PER VISIBLE SATELLITE IMAGERY. THE INCREASE     IN LARGE-SCALE ASCENT...AND LOW-LEVEL ASCENT ASSOCIATED WITH THE     FRONT...SHOULD ALSO AID IN CONVECTIVE DEVELOPMENT INTO MID     AFTERNOON.          THE INFLUX OF STEEP MID-LEVEL LAPSE RATES -- E.G. 8 C/KM WITHIN THE     700-500-MB LAYER PER UPSTREAM 12Z BOISE RAOB -- WILL CONTRIBUTE TO     THE DEVELOPMENT OF MLCAPE VALUES OF 400-900 J/KG ACROSS A LARGE PART     OF ERN MT AND S-CNTRL MT AHEAD OF THE FRONT...AND SUPPORT THE     INTENSIFICATION OF STORMS. WHILE THE AFOREMENTIONED CLOUDS MAY     HINDER DESTABILIZATION TO SOME DEGREE IN PARTS OF SERN MT...THE     STEEP NATURE OF THE LAPSE RATES COMBINED WITH MAINTENANCE OF MODEST     LOW-LEVEL MOISTURE -- I.E. SFC DEWPOINTS IN THE UPPER 40S TO LOWER     50S -- SHOULD STILL SUPPORT MARGINAL DESTABILIZATION IN THESE AREAS.     ALSO...MODERATE/STRONG MID-LEVEL FLOW WILL SUPPORT 30-45 KT OF     EFFECTIVE BULK SHEAR. THESE FACTORS COULD PROMOTE ORGANIZED STORM     STRUCTURES/CLUSTERS/LINE SEGMENTS CAPABLE OF PRODUCING DMGG WIND     GUSTS AND SVR HAIL AS STORMS MOVE TOWARD ERN MT BY EARLY EVENING.          ..COHEN/CARBIN.. 06/02/2012               ATTN...WFO...BYZ...GGW...TFX...