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URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 553

NWS STORM PREDICTION CENTER NORMAN OK

215 PM CDT FRI AUG 3 2012



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       PARTS OF WESTERN MINNESOTA

       EAST CENTRAL AND SOUTHEAST NORTH DAKOTA

       EASTERN SOUTH DAKOTA



EFFECTIVE THIS FRIDAY AFTERNOON AND EVENING FROM 215 PM UNTIL 900

PM CDT.



HAIL TO 1.5 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 75

STATUTE MILES EAST AND WEST OF A LINE FROM 30 MILES NORTHWEST OF

GRAND FORKS NORTH DAKOTA TO 55 MILES SOUTH OF MITCHELL 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 552...



DISCUSSION...THUNDERSTORMS WILL INCREASE IN COVERAGE/INTENSITY

ACROSS THE CENTRAL/ERN DAKOTAS THROUGH THE AFTERNOON INVOF A SURFACE

COLD FRONT...AND IN ADVANCE OF A STRONG MIDLEVEL TROUGH.  CONTINUED

SURFACE HEATING AND BOUNDARY LAYER DEWPOINTS IN THE 60S WILL

CONTRIBUTE TO MODERATE INSTABILITY /MLCAPE NEAR 2000 J PER

KG/...WHILE INCREASING MIDLEVEL FLOW WILL RESULT IN EFFECTIVE BULK

SHEAR AOA 40 KT.  THE ENVIRONMENT WILL SUPPORT SUPERCELLS WITH THE

INITIAL STORM DEVELOPMENT...THOUGH UPSCALE GROWTH INTO CLUSTERS/LINE

SEGMENTS APPEARS LIKELY LATER THIS AFTERNOON/EVENING.  LARGE HAIL

AND DAMAGING WINDS WILL BE THE PRIMARY SEVERE STORM THREATS.  AN

ISOLATED TORNADO OR TWO CANNOT BE RULED OUT GIVEN THE POTENTIAL FOR

EMBEDDED SUPERCELLS...BUT RATHER MODEST LOW-LEVEL MOISTURE FOR EARLY

AUGUST AND A PREDOMINANTLY LINEAR CONVECTIVE MODE SUGGEST THE

TORNADO RISK WILL REMAIN SOMEWHAT LIMITED.



AVIATION...A FEW SEVERE THUNDERSTORMS WITH HAIL SURFACE AND ALOFT

TO 1.5 INCHES. EXTREME TURBULENCE AND SURFACE WIND GUSTS TO 60

KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 550. MEAN STORM

MOTION VECTOR 26030.





...THOMPSON

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