

000 

WWUS20 KWNS 292225

SEL7

SPC WW 292225

IAZ000-NEZ000-SDZ000-300400-



URGENT - IMMEDIATE BROADCAST REQUESTED

TORNADO WATCH NUMBER 387

NWS STORM PREDICTION CENTER NORMAN OK

525 PM CDT THU MAY 29 2008



THE NWS STORM PREDICTION CENTER HAS ISSUED A

TORNADO WATCH FOR PORTIONS OF



       EXTREME NORTHWEST IOWA

       EXTREME NORTHEAST NEBRASKA

       SOUTHEAST SOUTH DAKOTA



EFFECTIVE THIS THURSDAY AFTERNOON AND EVENING FROM 525 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 35 STATUTE

MILES NORTH AND SOUTH OF A LINE FROM 70 MILES WEST NORTHWEST OF

YANKTON SOUTH DAKOTA TO 30 MILES NORTHEAST OF SIOUX CITY IOWA.

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 384...WW 385...WW 386...



DISCUSSION...VISIBLE SATELLITE IMAGERY AND SURFACE OBSERVATIONS

SUGGEST THAT THE WARM FRONT IS LIFTING SLOWLY N OF THE MO RIVER FROM

NEB INTO SD.  CONVECTIVE INITIATION WILL BECOME MORE PROBABLE IN THE

NEXT COUPLE OF HOURS ACROSS SE SD AS THE LOW LEVELS

WARM/MOISTEN...WHILE VERTICAL SHEAR IS ALREADY FAVORABLE FOR

SUPERCELLS.  A COUPLE OF TORNADOES WILL BE POSSIBLE WITH

SURFACE-BASED SUPERCELLS ALONG THE WARM FRONT...ALONG WITH LARGE

HAIL/DAMAGING WINDS THROUGH LATE EVENING.



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 26030.





...THOMPSON

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