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000 

WWUS20 KWNS 252103

SEL5

SPC WW 252103

MTZ000-WYZ000-260300-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 605

NWS STORM PREDICTION CENTER NORMAN OK

305 PM MDT WED JUN 25 2008



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       SOUTH CENTRAL AND SOUTHEAST MONTANA

       NORTH CENTRAL AND NORTHEAST WYOMING



EFFECTIVE THIS WEDNESDAY AFTERNOON AND EVENING FROM 305 PM UNTIL

900 PM MDT.



HAIL TO 2 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 80

STATUTE MILES EAST AND WEST OF A LINE FROM 75 MILES NORTH

NORTHEAST OF BILLINGS MONTANA TO 60 MILES SOUTH SOUTHEAST OF

GILLETTE WYOMING.  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.



DISCUSSION...SCATTERED THUNDERSTORMS ARE BEGINNING TO DEVELOP FROM

CENTRAL/SRN MT INTO NRN WY AS THE LOW LEVELS DESTABILIZE WITH

DAYTIME HEATING...AND AS A WEAK MID-UPPER SPEED MAX MOVES EWD OVER

MT.  MLCAPE VALUES AROUND 1500 J/KG IN CONJUNCTION WITH 0-6 KM BULK

SHEAR OF 35-45 KT WILL SUPPORT A THREAT FOR SUPERCELLS THROUGH THE

EVENING HOURS.  STEEP LAPSE RATES AND ONLY MODEST LOW-LEVEL MOISTURE

SUGGEST THAT LARGE HAIL AND DAMAGING WINDS WILL BE THE PRIMARY

SEVERE THREATS.



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

TO 2 INCHES. EXTREME TURBULENCE AND SURFACE WIND GUSTS TO 60

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

MOTION VECTOR 28025.





...THOMPSON

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