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101 

WWUS20 KWNS 252109

SEL8

SPC WW 252109

MTZ000-SDZ000-WYZ000-260500-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 428

NWS STORM PREDICTION CENTER NORMAN OK

310 PM MDT MON JUN 25 2012



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       SOUTHEAST MONTANA

       WESTERN SOUTH DAKOTA

       EASTERN WYOMING



EFFECTIVE THIS MONDAY AFTERNOON AND EVENING FROM 310 PM UNTIL

1100 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 70

STATUTE MILES EAST AND WEST OF A LINE FROM 40 MILES NORTHWEST OF

MILES CITY MONTANA TO 135 MILES SOUTHEAST OF GILLETTE WYOMING.

FOR A COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH

OUTLINE UPDATE (WOUS64 KWNS WOU8).



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 426...WW 427...



DISCUSSION...TSTMS ARE DEVELOPING THIS AFTERNOON ALONG THE HIGH

TERRAIN WITHIN A HOT...DEEPLY MIXED BOUNDARY LAYER...PERHAPS IN

RESPONSE TO A WEAK MIDLEVEL IMPULSE CRESTING RIDGE AXIS.  AIR MASS

MOISTENS/DESTABILIZES WITH EWD/NEWD EXTENT ACROSS THE WATCH

AREA...THOUGH CAP ALSO INCREASES.  SHOULD STORMS BECOME ROOTED IN

THE PROGRESSIVELY MORE UNSTABLE ENVIRONMENT...THE PRESENCE OF 30-40

KT OF DEEP-LAYER SHEAR WILL SUPPORT ORGANIZED STORM STRUCTURES

INCLUDING SUPERCELLS WITH A RISK FOR DAMAGING WINDS AND LARGE HAIL.



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 27020.





...MEAD

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