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URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 533

NWS STORM PREDICTION CENTER NORMAN OK

425 PM MDT FRI JUL 27 2012



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       WESTERN SOUTH DAKOTA



EFFECTIVE THIS FRIDAY AFTERNOON FROM 425 PM UNTIL MIDNIGHT 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 65

STATUTE MILES EAST AND WEST OF A LINE FROM 90 MILES NORTH

NORTHEAST OF RAPID CITY SOUTH DAKOTA TO 70 MILES SOUTH SOUTHEAST

OF RAPID CITY SOUTH DAKOTA.  FOR A COMPLETE DEPICTION OF THE

WATCH SEE THE ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU3).



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 531...WW 532...



DISCUSSION...WIDELY SCATTERED TSTMS ARE ANTICIPATED TO DEVELOP

ACROSS THE WATCH AREA THIS EVENING IN ADVANCE OF A WEAK MIDLEVEL

IMPULSE CRESTING MEAN RIDGE AXIS.  AIR MASS IS CHARACTERIZED BY

STEEP LOW TO MIDLEVEL LAPSE RATES AND A DEEPLY MIXED BOUNDARY LAYER.

 WHEN COUPLED WITH AROUND 40 KT OF DEEP-LAYER SHEAR...SETUP WILL

PROMOTE HIGH-BASED SUPERCELLS WHICH MAY TRANSITION TO A SMALL MCS

THIS EVENING WITH THE PRIMARY HAZARDS BEING DAMAGING WINDS AND SOME

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 27025.





...MEAD

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