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739 

WWUS20 KWNS 182342

SEL7

SPC WW 182342

IAZ000-MOZ000-NEZ000-190500-



URGENT - IMMEDIATE BROADCAST REQUESTED

TORNADO WATCH NUMBER 787

NWS STORM PREDICTION CENTER NORMAN OK

640 PM CDT THU AUG 18 2011



THE NWS STORM PREDICTION CENTER HAS ISSUED A

TORNADO WATCH FOR PORTIONS OF



       EXTREME SOUTHWEST IOWA

       NORTHWEST MISSOURI

       NORTHERN AND EASTERN NEBRASKA



EFFECTIVE THIS THURSDAY NIGHT FROM 640 PM UNTIL MIDNIGHT CDT.



TORNADOES...HAIL TO 3 INCHES IN DIAMETER...THUNDERSTORM WIND

GUSTS TO 80 MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE

AREAS.



THE TORNADO WATCH AREA IS APPROXIMATELY ALONG AND 100 STATUTE

MILES EAST AND WEST OF A LINE FROM 30 MILES NORTH NORTHEAST OF

AINSWORTH NEBRASKA TO 30 MILES WEST OF FALLS CITY NEBRASKA.  FOR

A COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH

OUTLINE UPDATE (WOUS64 KWNS WOU7).



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 785...WW 786...



DISCUSSION...SEVER STORMS OVER NERN NEB ARE TRACKING SEWD ALONG

OUTFLOW BOUNDARY FROM EARLIER SEVERE STORMS...WHERE PRONOUNCED

VEERING WIND PROFILES /REF OAX VAD DISPLAY/ ARE RESULTING IN

SUBSTANTIAL DEEP LAYER SHEAR AND EFFECTIVE SRH.  THIS WILL ENHANCE

THREAT FOR SUPERCELLS WITH POTENTIAL TO PRODUCE A FEW TORNADOES.

OTHER STRONG SUPERCELLS WITH TORNADO POTENTIAL ARE OVER EXTREME

SOUTHWEST IA AND WILL MOVE INTO NWRN MO SOON...WHILE ADDITIONAL

STORMS ARE LIKELY TO SPREAD FROM SD INTO INCREASINGLY MOIST/UNSTABLE

AIR MASS OVER NRN NEB OVER THE NEXT SEVERAL HOURS.



AVIATION...TORNADOES AND A FEW SEVERE THUNDERSTORMS WITH HAIL

SURFACE AND ALOFT TO 3 INCHES. EXTREME TURBULENCE AND SURFACE

WIND GUSTS TO 70 KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO

600. MEAN STORM MOTION VECTOR 31025.





...WEISS

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