WATCHES: Severe Thunderstorm Watch Number 677

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

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