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363 

WWUS20 KWNS 081921

SEL5

SPC WW 081921

IAZ000-090100-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 565

NWS STORM PREDICTION CENTER NORMAN OK

220 PM CDT WED AUG 8 2012



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       CENTRAL AND SOUTH CENTRAL IOWA



EFFECTIVE THIS WEDNESDAY AFTERNOON AND EVENING FROM 220 PM UNTIL

800 PM CDT.



HAIL TO 1.5 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 60

STATUTE MILES EAST AND WEST OF A LINE FROM 50 MILES NORTH

NORTHWEST OF DES MOINES IOWA TO 15 MILES EAST OF LAMONI IOWA.

FOR A COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH

OUTLINE UPDATE (WOUS64 KWNS WOU5).



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.



DISCUSSION...A CLUSTER OF STRONG/SEVERE STORMS WILL LIKELY INCREASE

IN COVERAGE/INTENSITY THIS AFTERNOON ACROSS IA...IN ADVANCE OF A

SEWD-MOVING MIDLEVEL TROUGH.  STEEP LAPSE RATES AND SURFACE HEATING

IN THE WAKE OF MORNING CLOUDS HAVE RESULTED IN MLCAPE IN EXCESS OF

1500 J/KG...IN AN ENVIRONMENT WITH SUFFICIENT VERTICAL SHEAR FOR

ORGANIZED MULTICELL CLUSTERS.  THE PRIMARY SEVERE RISKS WILL BE

DAMAGING WINDS AND LARGE HAIL THROUGH THIS EVENING.



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

TO 1.5 INCHES. EXTREME TURBULENCE AND SURFACE WIND GUSTS TO 60

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

MOTION VECTOR 31025.





...THOMPSON

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