WATCHES: Severe Thunderstorm Watch Number 515

WWUS20 KWNS 222054
SEL5
SPC WW 222054
IAZ000-ILZ000-WIZ000-230300-

URGENT - IMMEDIATE BROADCAST REQUESTED
SEVERE THUNDERSTORM WATCH NUMBER 515
NWS STORM PREDICTION CENTER NORMAN OK
350 PM CDT THU JUL 22 2010

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

IOWA
EXTREME NORTHWEST ILLINOIS
EXTREME SOUTHWEST WISCONSIN

EFFECTIVE THIS THURSDAY AFTERNOON AND EVENING FROM 350 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 60
STATUTE MILES NORTH AND SOUTH OF A LINE FROM 25 MILES NORTHEAST
OF DUBUQUE IOWA TO 70 MILES SOUTHWEST OF FORT DODGE IOWA. FOR A
COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH OUTLINE
UPDATE (WOUS64 KWNS WOU5).

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 514...

DISCUSSION...THUNDERSTORMS ARE DEVELOPING SWWD ALONG A LOW-LEVEL
CONVERGENCE BOUNDARY FROM SWRN WI INTO NRN IA...AND STORMS WILL
LIKELY CONTINUING FORMING ACROSS N CNTRL/CNTRL IA WITHIN THE NEXT
FEW HOURS. AIR MASS BECOME VERY UNSTABLE WITH MLCAPE OF 2000-3000
J/KG AS STRONG HEATING HAS OCCURRED THIS AFTERNOON. CONVECTION IS
LOCATED ALONG THE SRN EDGE OF STRONGER WINDS ALOFT...WITH 30-40 KT
UNIDIRECTIONAL SWLY WINDS PROVIDING SUFFICIENT SHEAR TO ENHANCE
SEVERE THUNDERSTORM THREAT. DAMAGING WIND GUSTS AND LARGE HAIL ARE
THE PRIMARY THREATS...ALTHOUGH A BRIEF TORNADO MAY ALSO BE POSSIBLE
WITH INITIAL DISCRETE STORMS.

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 24035.

...WEISS

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