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357 

WWUS20 KWNS 050414

SEL8

SPC WW 050414

IAZ000-MNZ000-050900-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 618

NWS STORM PREDICTION CENTER NORMAN OK

1115 PM CDT TUE SEP 4 2012



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       NORTHEAST IOWA

       EXTREME SOUTHEAST MINNESOTA



EFFECTIVE THIS TUESDAY NIGHT AND WEDNESDAY MORNING FROM 1115 PM

UNTIL 400 AM 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 40

STATUTE MILES NORTH AND SOUTH OF A LINE FROM 45 MILES NORTHWEST

OF WATERLOO IOWA TO 75 MILES EAST NORTHEAST OF WATERLOO IOWA.

FOR A COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH

OUTLINE UPDATE (WOUS64 KWNS WOU8).



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 615...WW 616...WW 617...



DISCUSSION...ELEVATED STORMS WILL LIKELY PERSIST IN THE WAA REGIME

ABOVE THE SHALLOW COLD POOL ACROSS NE IA...WHILE ADDITIONAL STORMS

MOVE INTO THIS SAME AREA FROM N CENTRAL IA IN THE NEXT COUPLE OF

HOURS.  MODERATE INSTABILITY REMAINS INVOF THE OUTFLOW

BOUNDARY...AND VERTICAL SHEAR IS SUFFICIENT FOR ORGANIZED SEVERE

STORMS.  THUS...THE RISK FOR AT LEAST ISOLATED LARGE HAIL/DAMAGING

WINDS IS EXPECTED TO CONTINUE FOR A FEW MORE HOURS.



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 500. MEAN STORM

MOTION VECTOR 29025.





...THOMPSON

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