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475 

WWUS20 KWNS 081821

SEL0

SPC WW 081821

IAZ000-090100-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 270

NWS STORM PREDICTION CENTER NORMAN OK

125 PM CDT FRI MAY 8 2009



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       MUCH OF IOWA



EFFECTIVE THIS FRIDAY AFTERNOON AND EVENING FROM 125 PM UNTIL 800

PM CDT.



HAIL TO 2 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 80

STATUTE MILES NORTH AND SOUTH OF A LINE FROM 25 MILES SOUTH

SOUTHWEST OF DENISON IOWA TO 50 MILES NORTH NORTHEAST OF OTTUMWA

IOWA.  FOR A COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED

WATCH OUTLINE UPDATE (WOUS64 KWNS WOU0).



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 267...WW 268...WW 269...



DISCUSSION...STRONG S/WV TROUGH AND JET MAX MOVING RAPIDLY EWD

ACROSS NEB WILL PROVIDE SHEAR AND ASCENT TO DEVELOP SEVERE

THUNDERSTORMS ACROSS WATCH AREA WHERE AIR MASS IS MODESTLY MOIST AND

UNSTABLE.  PRIMARY THREAT INITIALLY WILL BE LARGE HAIL WITH WIND

DAMAGE INCREASING DURING THE AFTERNOON AS STORMS DEVELOP UPSCALE

INTO BOWS AND LINE SEGMENTS.



AVIATION...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 450. MEAN STORM

MOTION VECTOR 27030.





...HALES

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