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336 

WWUS20 KWNS 241954

SEL7

SPC WW 241954

COZ000-MTZ000-NEZ000-SDZ000-WYZ000-250300-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 547

NWS STORM PREDICTION CENTER NORMAN OK

155 PM MDT FRI JUN 24 2011



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       NORTHEAST COLORADO

       SOUTHEAST MONTANA

       WESTERN NEBRASKA PANHANDLE

       WESTERN SOUTH DAKOTA

       CENTRAL AND EASTERN WYOMING



EFFECTIVE THIS FRIDAY AFTERNOON AND EVENING FROM 155 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 105

STATUTE MILES EAST AND WEST OF A LINE FROM 45 MILES SOUTH OF

CHEYENNE WYOMING TO 40 MILES NORTH NORTHEAST OF BROADUS 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 544...WW 545...WW 546...



DISCUSSION...TSTMS ARE DEVELOPING ALONG THE FAVORED TERRAIN OF WY

THIS AFTERNOON IN ADVANCE OF MIDLEVEL IMPULSE APPROACHING FROM THE

W.  A FURTHER INCREASE IN LARGE-SCALE FORCING AND LOW-LEVEL UPSLOPE

FLOW SHOULD SUPPORT ADDITIONAL STORM DEVELOPMENT ACROSS PARTS OF

NERN CO...SERN MT AND WRN SD.  GIVEN THE PRESENCE OF STEEP LAPSE

RATES...BOUNDARY-LAYER DEWPOINTS IN THE 50S AND 40-50 KT OF DEEP WLY

SHEAR...SETUP WILL FAVOR THE DEVELOPMENT OF SUPERCELLS CAPABLE OF

MAINLY LARGE HAIL AND DAMAGING WINDS.  WHILE A TORNADO IS POSSIBLE

LATE THIS AFTERNOON INTO EVENING...A RELATIVELY WEAK LOW-LEVEL WIND

FIELD /AND RESULTANT MARGINAL NEAR-GROUND SPEED SHEAR/ IS EXPECTED

TO PRECLUDE A MORE ROBUST 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 500. MEAN STORM

MOTION VECTOR 25030.





...MEAD

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