

486 

WWUS20 KWNS 211831

SEL7

SPC WW 211831

IAZ000-ILZ000-MOZ000-WIZ000-LMZ000-220200-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 677

NWS STORM PREDICTION CENTER NORMAN OK

130 PM CDT TUE SEP 21 2010



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       SOUTHEAST IOWA

       NORTHERN ILLINOIS

       FAR NORTHEAST MISSOURI

       FAR SOUTHERN WISCONSIN

       LAKE MICHIGAN



EFFECTIVE THIS TUESDAY AFTERNOON AND EVENING FROM 130 PM UNTIL

900 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 NORTH AND SOUTH OF A LINE FROM 60 MILES SOUTH

SOUTHWEST OF CEDAR RAPIDS IOWA TO 55 MILES EAST OF ROCKFORD

ILLINOIS.  FOR A COMPLETE DEPICTION OF THE WATCH SEE THE

ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU7).



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 676...



DISCUSSION...TSTMS DEVELOPING OVER PARTS OF ERN/SERN IA SHOULD

CONTINUE TO INTENSIFY THIS AFTERNOON WHILE PROGRESSING EWD/SEWD

THROUGH A MOIST AND MODERATELY UNSTABLE AIR MASS WITH MLCAPE OF

1000-2000 J/KG.  REGIONAL PROFILER AND VWP DATA SHOW THAT MODESTLY

STRONG UNIDIRECTIONAL TROPOSPHERIC FLOW IS IN PLACE ACROSS THE WARM

SECTOR WHICH WILL BE SUPPORTIVE OF UPSCALE GROWTH OF STORMS INTO ONE

OR MORE MCS/S WITH THE PRIMARY HAZARDS BEING DAMAGING WIND GUSTS AND

HAIL.



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 27035.





...MEAD

