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367 

WWUS20 KWNS 222249

SEL3

SPC WW 222249

MNZ000-NDZ000-SDZ000-230600-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 503

NWS STORM PREDICTION CENTER NORMAN OK

545 PM CDT SUN JUL 22 2012



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       EXTREME WESTERN MINNESOTA

       SOUTHEAST NORTH DAKOTA

       NORTHERN AND NORTHEAST SOUTH DAKOTA



EFFECTIVE THIS SUNDAY AFTERNOON AND MONDAY MORNING FROM 545 PM

UNTIL 100 AM CDT.



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 40

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

MOBRIDGE SOUTH DAKOTA TO 10 MILES NORTH OF ORTONVILLE MINNESOTA.

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 502...



DISCUSSION...SEVERAL ROBUST STORMS HAVE ERUPTED ALONG A SLOW MOVING

COLD FRONT ALIGNED WITH THE ND/SD BORDER LATE THIS AFTERNOON.

DESPITE PRONOUNCED MID LEVEL WARM LAYER...SUFFICIENT BOUNDARY LAYER

HEATING AND COMBINATION OF PERSISTENT CONVERGENCE ALONG THE FRONT

AND MOIST AXIS IN THIS AREA...AS WELL AS SUBTLE HEIGHT FALLS

ASSOCIATED WITH AN UPPER SHORT WAVE TROUGH IN CANADA...HAVE ALL

CONTRIBUTED TO THE RECENT INCREASE IN STORM DEVELOPMENT AND

COVERAGE. MODEL GUIDANCE IS NOT CONSISTENT WITH THIS CURRENT

DEVELOPMENT SUGGESTING GREATER UNCERTAINTY IN BOTH STORM PERSISTENCE

AND EVOLUTION. HOWEVER...MAGNITUDE OF CAPE AHEAD OF THE FRONT AND

ONGOING ACTIVITY...ALONG WITH MODEST EFFECTIVE SHEAR SUPPORTIVE OF

SUPERCELL STORM STRUCTURE AND UPDRAFT PERSISTENCE...WARRANT THE

ISSUANCE OF A WATCH. THESE STORMS WILL HAVE THE POTENTIAL TO PRODUCE

HAIL OF 1-2 INCHES IN DIAMETER AND DOWNBURST WINDS TO 60KT.



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 600. MEAN STORM

MOTION VECTOR 30020.





...CARBIN

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