

614 

WWUS20 KWNS 052053

SEL0

SPC WW 052053

MTZ000-WYZ000-060200-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 730

NWS STORM PREDICTION CENTER NORMAN OK

255 PM MDT FRI AUG 5 2011



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       SOUTHEAST MONTANA

       NORTHEAST WYOMING



EFFECTIVE THIS FRIDAY AFTERNOON AND EVENING FROM 255 PM UNTIL 800

PM MDT.



HAIL TO 1.5 INCHES IN DIAMETER...THUNDERSTORM WIND GUSTS TO 70

MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE AREAS.



THE SEVERE THUNDERSTORM WATCH AREA IS APPROXIMATELY ALONG AND 70

STATUTE MILES EAST AND WEST OF A LINE FROM 10 MILES NORTHWEST OF

MILES CITY MONTANA TO 10 MILES SOUTH SOUTHWEST OF GILLETTE

WYOMING.  FOR A COMPLETE DEPICTION OF THE WATCH SEE THE

ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU0).



REMEMBER...A SEVERE THUNDERSTORM WATCH MEANS CONDITIONS ARE

FAVORABLE FOR SEVERE THUNDERSTORMS IN AND CLOSE TO THE WATCH

AREA. PERSONS IN THESE AREAS SHOULD BE ON THE LOOKOUT FOR

THREATENING WEATHER CONDITIONS AND LISTEN FOR LATER STATEMENTS

AND POSSIBLE WARNINGS. SEVERE THUNDERSTORMS CAN AND OCCASIONALLY

DO PRODUCE TORNADOES.



OTHER WATCH INFORMATION...CONTINUE...WW 729...



DISCUSSION...HIGH-BASED TSTMS HAVE BEGUN TO FORM ALONG THE HIGHER

TERRAIN OF SERN MT AND NRN WY AS PRIMARY UPR TROUGH AND ASSOCIATED

ASCENT SPREADS EWD.  LLVL AND INCREASINGLY MOIST UPSLOPE FLOW

DOWNSTREAM ACROSS THE LOWER PLAINS AND ADJACENT BLACK HILLS/BIG HORN

MOUNTAINS WILL LIKELY CONTRIBUTE TO DEEPENING STORMS.  STORMS WILL

LIKELY FORM INTO LINEAR SEGMENTS PRODUCING HIGH WINDS AND POSSIBLY

HAIL THROUGH THE EARLY EVENING HOURS.  ISOLD SUPERCELLS WILL BE

POSSIBLE...ESPECIALLY EARLY IN STORM LIFE CYCLES...BUT PRIMARILY

BOWS/LEWPS WILL BE THE FAVORED MODE.



AVIATION...A FEW SEVERE THUNDERSTORMS WITH HAIL SURFACE AND ALOFT

TO 1.5 INCHES. EXTREME TURBULENCE AND SURFACE WIND GUSTS TO 60

KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 400. MEAN STORM

MOTION VECTOR 25035.





...RACY

