

000 

WWUS20 KWNS 211428

SEL3

SPC WW 211428

IAZ000-MNZ000-SDZ000-212100-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 433

NWS STORM PREDICTION CENTER NORMAN OK

930 AM CDT THU JUN 21 2007



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       NORTHWEST IOWA

       SOUTHWEST MINNESOTA

       SOUTHEAST SOUTH DAKOTA



EFFECTIVE THIS THURSDAY MORNING AND AFTERNOON FROM 930 AM UNTIL

400 PM CDT.



HAIL TO 2.5 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 55

STATUTE MILES NORTH AND SOUTH OF A LINE FROM 60 MILES WEST OF

MITCHELL SOUTH DAKOTA TO 20 MILES NORTH NORTHEAST OF SPENCER

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

WATCH OUTLINE UPDATE (WOUS64 KWNS WOU3).



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 431...WW 432...



DISCUSSION...MCS EXPECTED TO EXPAND IN COVERAGE AND INTENSITY ALONG

NOSE OF MODEST SWLY LLJ AND INVOF SURFACE FRONT STALLED ACROSS THE

REGION.  AIR MASS WILL BECOME MODERATE TO STRONGLY UNSTABLE SOUTH OF

THE FRONT WITH SHEAR SUPPORTIVE OF SUPERCELLS AND POSSIBLE EVOLUTION

INTO LINEAR MCS/BOW ECHO.  VERY LARGE HAIL MAY ACCOMPANY MORE

DISCRETE STORMS WITH POTENTIAL FOR DAMAGING WINDS EXPANDING WITH

TIME INTO THE EARLY AFTERNOON.



AVIATION...A FEW SEVERE THUNDERSTORMS WITH HAIL SURFACE AND ALOFT

TO 2.5 INCHES. EXTREME TURBULENCE AND SURFACE WIND GUSTS TO 60

KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 500. MEAN STORM

MOTION VECTOR 31030.





...EVANS

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