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WWUS20 KWNS 042246

SEL1

SPC WW 042246

IAZ000-NEZ000-050500-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 241

NWS STORM PREDICTION CENTER NORMAN OK

550 PM CDT FRI MAY 4 2012



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       EXTREME WEST CENTRAL AND SOUTHWEST IOWA

       CENTRAL AND EASTERN NEBRASKA



EFFECTIVE THIS FRIDAY AFTERNOON FROM 550 PM UNTIL MIDNIGHT 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 35 MILES SOUTH OF

BURWELL NEBRASKA TO 35 MILES NORTH NORTHEAST OF SHENANDOAH IOWA.

FOR A COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH

OUTLINE UPDATE (WOUS64 KWNS WOU1).



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 238...WW 239...WW 240...



DISCUSSION...THUNDERSTORM COVERAGE/INTENSITY IS EXPECTED TO INCREASE

ALONG A SWD-MOVING OUTFLOW BOUNDARY ACROSS CENTRAL/ERN NEB THROUGH

LATE EVENING.  STRONG INSTABILITY IS PRESENT S OF THE BOUNDARY...AND

DEEP-LAYER VERTICAL SHEAR IS SUFFICIENT FOR SUPERCELLS.  LARGE HAIL

AND DAMAGING WINDS WILL BE THE PRIMARY THREATS GIVEN THE STEEP

LOW-MIDLEVEL LAPSE RATES ACROSS THE AREA.



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 550. MEAN STORM

MOTION VECTOR 30015.





...THOMPSON

