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119 

WWUS20 KWNS 110101

SEL9

SPC WW 110101

IAZ000-MNZ000-NEZ000-SDZ000-110800-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 449

NWS STORM PREDICTION CENTER NORMAN OK

800 PM CDT SAT JUL 10 2010



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       EXTREME NORTHWEST IOWA

       SOUTHWEST MINNESOTA

       NORTHEAST NEBRASKA

       SOUTHEAST SOUTH DAKOTA



EFFECTIVE THIS SATURDAY NIGHT AND SUNDAY MORNING FROM 800 PM

UNTIL 300 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 70

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

NORTHEAST OF ORTONVILLE MINNESOTA TO 20 MILES SOUTH SOUTHWEST OF

NORFOLK NEBRASKA.  FOR A COMPLETE DEPICTION OF THE WATCH SEE THE

ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU9).



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...THIS SEVERE THUNDERSTORM WATCH REPLACES

TORNADO WATCH NUMBER 448. WATCH NUMBER 448 WILL NOT BE IN EFFECT

AFTER 800 PM CDT. CONTINUE...WW 446...WW 447...



DISCUSSION...SEVERAL CLUSTERS OF STRONG/SEVERE THUNDERSTORMS WILL

PERSIST OVERNIGHT AS AN EMBEDDED SHORTWAVE TROUGH MOVES ESEWD FROM

SW SD AND ENCOUNTERS A REMAINING CORRIDOR OF STRONG INSTABILITY FROM

ERN NEB INTO SW MN.  THE COMBINATION OF EFFECTIVE BULK SHEAR IN

EXCESS OF 30 KT AND MLCAPE OF 1500-3000 J/KG WILL SUPPORT ORGANIZED

CLUSTERS WITH DAMAGING WINDS AND LARGE HAIL...BEFORE THE CONVECTION

MOVES E OF THE STRONGER INSTABILITY DURING THE EARLY MORNING HOURS.



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 31015.





...THOMPSON

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