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WWUS20 KWNS 052100

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SPC WW 052100

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URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 658

NWS STORM PREDICTION CENTER NORMAN OK

400 PM CDT SAT JUL 5 2008



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       NORTH CENTRAL AND CENTRAL NEBRASKA



EFFECTIVE THIS SATURDAY AFTERNOON AND EVENING FROM 400 PM UNTIL

1000 PM 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 55

STATUTE MILES EAST AND WEST OF A LINE FROM 35 MILES NORTH

NORTHEAST OF AINSWORTH NEBRASKA TO 40 MILES WEST SOUTHWEST OF

NORTH PLATTE NEBRASKA.  FOR A COMPLETE DEPICTION OF THE WATCH SEE

THE ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU8).



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.



DISCUSSION...THUNDERSTORMS HAVE DEVELOPED ALONG A SURFACE TROUGH

WHERE STRONG HEATING HAS ERODED THE CAP IN A NARROW CORRIDOR AND

CONTRIBUTED TO MLCAPE VALUES OF 1500-2500 J/KG.  VERTICAL SHEAR IS

MARGINALLY FAVORABLE FOR SUPERCELL STRUCTURES...WHICH WILL TEND TO

LOCALLY ENHANCE THE LARGE HAIL THREAT.  OTHERWISE...ASIDE FROM THE

POSSIBILITY OF AN ISOLATED TORNADO EARLY IN STORM

DEVELOPMENT...DAMAGING WINDS WILL BE POSSIBLE WITH THE STRONGER

STORMS AND MERGING CLUSTERS THROUGH LATE EVENING.



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

