

000 

WWUS20 KWNS 210427

SEL3

SPC WW 210427

IAZ000-ILZ000-MOZ000-211200-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 713

NWS STORM PREDICTION CENTER NORMAN OK

1125 PM CDT SUN JUL 20 2008



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       IOWA

       FAR NORTHWEST ILLINOIS

       EXTREME NORTHEAST MISSOURI



EFFECTIVE THIS SUNDAY NIGHT AND MONDAY MORNING FROM 1125 PM UNTIL

700 AM CDT.



HAIL TO 3 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 NORTH AND SOUTH OF A LINE FROM 55 MILES SOUTH OF

STORM LAKE IOWA TO 20 MILES SOUTH OF MOLINE ILLINOIS.  FOR A

COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH OUTLINE

UPDATE (WOUS64 KWNS WOU3).



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 711...WW 712...



DISCUSSION...DEEP MOIST CONVECTION WILL INCREASE ACROSS WW OVERNIGHT

AS SWLY LLJ INTERACTS WITH LOW LEVEL THETA-E GRADIENT EXTENDING

ESE-WNW FROM E-CENTRAL NEB INTO CENTRAL IL.  MCS NOW OVER NEB IS

FORECAST TO ACCELERATE ALONG THIS BOUNDARY INTO IA LATE

TONIGHT...WITH POTENTIAL FOR WIDESPREAD WIND DAMAGE ONCE IT

ORGANIZES ALONG A COMMON GUST FRONT.  ADDITIONAL DEVELOPMENT AHEAD

OF THIS FEATURE WILL ALSO POSE A THREAT OF LARGE HAIL...SOME OF

WHICH COULD BECOME QUITE LARGE.  THIS LEADING ACTIVITY COULD ALSO

FORM INTO A LARGER MCS OVERNIGHT AND TRACK SEWD INTO IL/FAR NERN MO.



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

TO 3 INCHES. EXTREME TURBULENCE AND SURFACE WIND GUSTS TO 60

KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 550. MEAN STORM

MOTION VECTOR 29035.





...EVANS

