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WWUS20 KWNS 201854

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SPC WW 201854

MTZ000-WYZ000-210100-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 357

NWS STORM PREDICTION CENTER NORMAN OK

155 PM CDT SUN JUN 20 2010



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       PARTS OF SOUTHERN MONTANA

       PARTS OF CENTRAL AND NORTHERN WYOMING



EFFECTIVE THIS SUNDAY AFTERNOON AND EVENING FROM 155 PM UNTIL 800

PM CDT.



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 60

STATUTE MILES EAST AND WEST OF A LINE FROM 50 MILES EAST

SOUTHEAST OF LANDER WYOMING TO 55 MILES EAST NORTHEAST OF

HARLOWTON MONTANA.  FOR A COMPLETE DEPICTION OF THE WATCH SEE THE

ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU7).



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 356...



DISCUSSION...THUNDERSTORMS WILL INCREASE IN NUMBER AND INTENSITY

WITH CONTINUED HEATING OF A MODERATELY UNSTABLE AIR MASS ACROSS THE

WATCH AREA. INITIAL STORMS OVER HIGHER TERRAIN BUT WITH STEEP LAPSE

RATES AND APPROACH OF UPPER S/WV FROM THE SW...STRONGER/SEVERE

STORMS WILL DEVELOP ACROSS THE WATCH WITH LARGE HAIL AND LOCAL

DAMAGING WINDS THE PRIMARY THREAT.



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 450. MEAN STORM

MOTION VECTOR 23025.





...HALES

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