

000 

WWUS20 KWNS 221958

SEL3

SPC WW 221958

IAZ000-NEZ000-230200-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 443

NWS STORM PREDICTION CENTER NORMAN OK

300 PM CDT FRI JUN 22 2007



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       WESTERN IOWA

       SOUTHEASTERN NEBRASKA



EFFECTIVE THIS FRIDAY AFTERNOON AND EVENING FROM 300 PM UNTIL 900

PM CDT.



HAIL TO 2.5 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 45

STATUTE MILES NORTH AND SOUTH OF A LINE FROM 75 MILES SOUTHWEST

OF COLUMBUS NEBRASKA TO 35 MILES SOUTH SOUTHEAST OF DENISON IOWA.

 FOR A COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH

OUTLINE UPDATE (WOUS64 KWNS WOU3).



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.



OTHER WATCH INFORMATION...CONTINUE...WW 442...



DISCUSSION...VERY UNSTABLE AIR MASS IN PLACE ALONG WEAK SURFACE

CONVERGENCE AXIS EXTENDING FROM W-CENTRAL IA INTO S-CENTRAL NEB.

DESPITE LACK OF UPPER SUPPORT/ENHANCEMENT...DIURNAL HEATING AND WEAK

CONVERGENCE MAY DRIVE ISOLATED THUNDERSTORM DEVELOPMENT LATE TODAY

ALONG THIS AXIS.  DEGREE OF INSTABILITY AND MODEST DEEP LAYER SHEAR

INDICATE STORMS MAY BECOME SEVERE QUITE RAPIDLY AND POSSIBLY DEVELOP

LOW TO MID LEVEL ROTATION.  PRIMARY THREATS ARE EXPECTED TO BE LARGE

HAIL AND ISOLATED DAMAGING WINDS FROM THE SLOW MOVING STORMS THIS

EVENING.



AVIATION...A FEW SEVERE THUNDERSTORMS WITH HAIL SURFACE AND ALOFT

TO 2.5 INCHES. EXTREME TURBULENCE AND SURFACE WIND GUSTS TO 60

KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 500. MEAN STORM

MOTION VECTOR 26015.





...EVANS

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