

109 

WWUS20 KWNS 302117

SEL5

SPC WW 302117

MTZ000-NDZ000-SDZ000-WYZ000-010400-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 535

NWS STORM PREDICTION CENTER NORMAN OK

320 PM MDT TUE JUN 30 2009



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       PARTS OF EASTERN MONTANA

       PARTS OF WESTERN NORTH DAKOTA

       PARTS OF WESTERN SOUTH DAKOTA

       PARTS OF NORTHEAST WYOMING



EFFECTIVE THIS TUESDAY AFTERNOON AND EVENING FROM 320 PM UNTIL

1000 PM MDT.



HAIL TO 2.5 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 60

STATUTE MILES EAST AND WEST OF A LINE FROM 60 MILES NORTH

NORTHWEST OF WILLISTON NORTH DAKOTA TO 45 MILES SOUTHWEST OF

RAPID CITY SOUTH DAKOTA.  FOR A COMPLETE DEPICTION OF THE WATCH

SEE THE ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU5).



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 533...WW 534...



DISCUSSION...AREA OF MDTLY UNSTABLE AIR MASS STRADDLES ND/MT BORDER

SWD TO BLACK HILLS.  WITH 30-40KT OF DEEP LAYER SHEAR AND LITTLE

REMAINING CINH...THUNDERSTORMS WILL INCREASE IN NUMBER AND INTENSITY

ACROSS WATCH AREA WITH A FEW SUPERCELLS DEVELOPING.  PRIMARY THREAT

WILL BE LARGE HAIL/DAMAGING DOWNBURSTS WINDS...PARTICULARLY

ASSOCIATED WITH ANY SUPERCELL.



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

TO 2.5 INCHES. EXTREME TURBULENCE AND SURFACE WIND GUSTS TO 60

KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 500. MEAN STORM

MOTION VECTOR 29025.





...HALES

