

229 

WWUS20 KWNS 181206

SEL0

SPC WW 181206

IAZ000-181600-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 460

NWS STORM PREDICTION CENTER NORMAN OK

700 AM CDT THU JUN 18 2009



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       NORTHERN IOWA



EFFECTIVE THIS THURSDAY MORNING FROM 700 AM UNTIL 1100 AM 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 50

STATUTE MILES NORTH AND SOUTH OF A LINE FROM 35 MILES WEST

NORTHWEST OF FORT DODGE IOWA TO 25 MILES NORTHEAST OF WATERLOO

IOWA.  FOR A COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED

WATCH OUTLINE UPDATE (WOUS64 KWNS WOU0).



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 457...WW 458...WW 459...



DISCUSSION...MATURE MCS/BOW MOVING GENERALLY EWD AT 50KT INTO NWRN

IA ATTM. FAVORABLE LARGE SCALE SUPPORT IN THE FORM OF A

LOW-AMPLITUDE SHORT

WAVE TROUGH...AND ABUNDANT WARM/MOIST AIR STREAMING INTO THE AREA ON

50-60KT LLJ...SHOULD MAINTAIN THE THREAT FOR WIND DAMAGE ALONG THE

LEADING EDGE OF THE BOW AS IT TRACKS ACROSS NRN IA OVER THE NEXT

COUPLE OF HOURS.



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 550. MEAN STORM

MOTION VECTOR 27045.





...CARBIN

