WATCHES: Severe Thunderstorm Watch Number 527

WWUS20 KWNS 271947
SEL7
SPC WW 271947
IAZ000-ILZ000-MOZ000-WIZ000-280300-

URGENT - IMMEDIATE BROADCAST REQUESTED
SEVERE THUNDERSTORM WATCH NUMBER 527
NWS STORM PREDICTION CENTER NORMAN OK
240 PM CDT SAT JUN 27 2009

THE NWS STORM PREDICTION CENTER HAS ISSUED A
SEVERE THUNDERSTORM WATCH FOR PORTIONS OF

EASTERN IOWA
NORTHERN ILLINOIS
EXTREME NORTHEASTERN MISSOURI
SOUTHERN WISCONSIN

EFFECTIVE THIS SATURDAY AFTERNOON AND EVENING FROM 240 PM UNTIL
1000 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 70
STATUTE MILES NORTH AND SOUTH OF A LINE FROM 35 MILES EAST
SOUTHEAST OF ROCKFORD ILLINOIS TO 55 MILES SOUTHWEST OF CEDAR
RAPIDS IOWA. 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 525...WW 526...

DISCUSSION...STORMS ARE EXPECTED TO INCREASE IN NUMBER AND INTENSITY
AS UPPER JET AND COLD FRONT SPREAD IN FROM THE WEST. AIR MASS OVER
IOWA HAS BECOME STRONGLY UNSTABLE AS TEMPERATURES HAVE WARMED INTO
THE LOWER 90S...WITH DEWPOINTS IN THE MID 70S. THIS AIR MASS WILL
SPREAD EWD INTO NRN IL AND SRN WI THROUGH THE AFTERNOON. THE DEGREE
OF INSTABILITY AND DEEP LAYER SHEAR INCREASING TO 30 TO 40 KT SHOULD
SUPPORT STORMS WITH SOME MID LEVEL ROTATION AND HAIL. ALSO...THE
STORMS MAY CONSOLIDATE INTO A LINE ALONG THE FRONT...AND GIVEN THE
UNIDIRECTIONAL WLY WINDS ABOVE THE BOUNDARY LAYER...DAMAGING WINDS
WOULD ALSO BE EXPECTED.

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 27025.

...IMY

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