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WWUS20 KWNS 061428

SEL6

SPC WW 061428

IAZ000-ILZ000-MOZ000-062200-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 256

NWS STORM PREDICTION CENTER NORMAN OK

930 AM CDT SUN MAY 6 2012



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       EASTERN IOWA

       NORTHWEST ILLINOIS

       FAR NORTHEAST MISSOURI



EFFECTIVE THIS SUNDAY MORNING AND AFTERNOON FROM 930 AM UNTIL 500

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 75

STATUTE MILES EAST AND WEST OF A LINE FROM 55 MILES EAST

NORTHEAST OF CEDAR RAPIDS IOWA TO 35 MILES SOUTH SOUTHEAST OF

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

ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU6).



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 255...



DISCUSSION...WHILE BOWING MCS OVER S-CNTRL IA APPEARS TO HAVE

TEMPORARILY WEAKENED...DOWNSTREAM AIR MASS ACROSS THE WATCH AREA IS

ALREADY VERY UNSTABLE WITH 12Z SOUNDINGS SHOWING MUCAPE VALUES OF

4000-5000 J/KG.  CONTINUED BOUNDARY LAYER HEATING ALONG STATIONARY

FRONT FROM SERN IA INTO CNTRL IL SHOULD ALLOW STORMS TO BECOME

PROGRESSIVELY SURFACE-BASED WITH AN INCREASED THREAT FOR DAMAGING

WINDS AND HAIL.



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 27030.





...MEAD

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