

284 

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

