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WWUS20 KWNS 071848

SEL8

SPC WW 071848

IAZ000-KSZ000-MOZ000-NEZ000-080100-



URGENT - IMMEDIATE BROADCAST REQUESTED

TORNADO WATCH NUMBER 258

NWS STORM PREDICTION CENTER NORMAN OK

145 PM CDT THU MAY 7 2009



THE NWS STORM PREDICTION CENTER HAS ISSUED A

TORNADO WATCH FOR PORTIONS OF



       PARTS OF SOUTHWEST IOWA

       PARTS OF NORTHEAST KANSAS

       LARGE PART OF NORTHERN MISSOURI

       PARTS OF SOUTHEAST NEBRASKA



EFFECTIVE THIS THURSDAY AFTERNOON AND EVENING FROM 145 PM UNTIL

800 PM CDT.



TORNADOES...HAIL TO 3 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 90 STATUTE

MILES NORTH AND SOUTH OF A LINE FROM 30 MILES WEST OF FALLS CITY

NEBRASKA TO 35 MILES SOUTH SOUTHEAST OF KIRKSVILLE MISSOURI.  FOR

A COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH

OUTLINE UPDATE (WOUS64 KWNS WOU8).



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.



DISCUSSION...LOW LEVEL MOISTURE AND INSTABILITY RETURNING RAPIDLY

ERN KS ON 30KT LLJ.  CONVERGENCE ALONG BOUNDARY SERN NEB EWD INTO

SWRN IA WILL BE FOCUS FOR STORM INITIATION.  STRONG VEERING SHEAR

PROFILES AND STEEP MID LEVEL LAPSE RATES SUPPORT RAPID DEVELOPMENT

OF STRONG/SEVERE THUNDERSTORMS VICINITY OF BOUNDARY.  SUPERCELLS

LIKELY...WHICH WILL THEN MOVE/DEVELOP E/SE INTO RETURNING

INSTABILITY.  VERY LARGE HAIL IS LIKELY WITH ANY SUPERCELL AND

TORNADO THREAT WILL INCREASE THRU THE AFTERNOON AS STORMS MOVE INTO

GREATER INSTABILITY.



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

SURFACE AND ALOFT TO 3 INCHES. EXTREME TURBULENCE AND SURFACE

WIND GUSTS TO 60 KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO

500. MEAN STORM MOTION VECTOR 30025.





...HALES

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