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URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 551

NWS STORM PREDICTION CENTER NORMAN OK

205 PM MDT THU AUG 2 2012



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       EASTERN MONTANA

       WESTERN NORTH DAKOTA

       NORTHWEST SOUTH DAKOTA

       NORTHEAST WYOMING



EFFECTIVE THIS THURSDAY AFTERNOON AND EVENING FROM 205 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 85

STATUTE MILES EAST AND WEST OF A LINE FROM 80 MILES EAST OF

GILLETTE WYOMING TO 50 MILES NORTHEAST OF WOLF POINT MONTANA.

FOR A COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH

OUTLINE UPDATE (WOUS64 KWNS WOU1).



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 550...



DISCUSSION...STORMS ARE INTENSIFYING OVER SERN MT AND NERN WY ALONG

A DRY LINE/CONVERGENCE ZONE...WHILE NEW CU/TCU IS EVIDENT IN

SATELLITE IMAGERY FARTHER NORTH INTO NERN MT WHERE LOW LEVEL

MOISTURE WITH SURFACE DEW POINTS REMAIN IN THE 50S.  INITIAL ARC OF

WARM ADVECTION CONVECTION FROM NERN MT INTO SWRN ND IS EXPECTED TO

PROGRESS EWD WITH ADDITIONAL STRONG/SEVERE STORMS DEVELOPING OVER

ERN MT AND NERN WY.  STEEP LAPSE RATES ARE CONTRIBUTING TO MLCAPE OF

1000-1500 J/KG...AND 30-40 KT WESTERLY MID LEVEL WINDS ARE RESULTING

IN SUFFICIENT DEEP LAYER SHEAR TO SUPPORT ORGANIZED SEVERE STORMS

INTO THE EVENING HOURS AS ACTIVITY SPREADS EWD.



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 27025.





...WEISS

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