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000 

WWUS20 KWNS 032015

SEL1

SPC WW 032015

NEZ000-SDZ000-040400-



URGENT - IMMEDIATE BROADCAST REQUESTED

TORNADO WATCH NUMBER 561

NWS STORM PREDICTION CENTER NORMAN OK

315 PM CDT FRI AUG 3 2007



THE NWS STORM PREDICTION CENTER HAS ISSUED A

TORNADO WATCH FOR PORTIONS OF



       CENTRAL NEBRASKA

       SOUTH CENTRAL SOUTH DAKOTA



EFFECTIVE THIS FRIDAY AFTERNOON AND EVENING FROM 315 PM UNTIL

1100 PM CDT.



TORNADOES...HAIL TO 2 INCHES IN DIAMETER...THUNDERSTORM WIND

GUSTS TO 70 MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE

AREAS.



THE TORNADO WATCH AREA IS APPROXIMATELY ALONG AND 75 STATUTE

MILES EAST AND WEST OF A LINE FROM 60 MILES NORTHWEST OF

VALENTINE NEBRASKA TO 40 MILES WEST OF BROKEN BOW NEBRASKA.  FOR

A COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH

OUTLINE UPDATE (WOUS64 KWNS WOU1).



REMEMBER...A TORNADO WATCH MEANS CONDITIONS ARE FAVORABLE FOR

TORNADOES AND 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.



OTHER WATCH INFORMATION...CONTINUE...WW 560...



DISCUSSION...AIR MASS CONTINUES TO DESTABILIZE ACROSS THE REGION

WITH MLCAPES ACHIEVING 1500-2000 J/KG. IN ADDITION WITH BROAD

SHORTWAVE TROUGH APPROACHING AREA...THERE IS AN INCREASE IN LOW/MID

LEVEL FLOW SUFFICIENT FOR DEEP LAYER SHEAR VALUES TO BE 40-45 KT

NEAR A BOUNDARY THAT IS JUST NORTH OF THE SD/NEB BORDER.  THIS HAS

LEAD TO THE DEVELOPMENT OF SOME HP SUPERCELLS ACROSS PARTS OF SRN

SD/NRN NEB WHICH ARE MOVING INTO THE INSTABILITY AXIS.  THERE IS A

THREAT FOR TORNADOES...BUT WOULD EXPECT HAIL AND DAMAGING WINDS TO

BE PREVALENT ACROSS THE AREA.



AVIATION...TORNADOES AND 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 27035.





...MCCARTHY

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