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WWUS20 KWNS 172256

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URGENT - IMMEDIATE BROADCAST REQUESTED

TORNADO WATCH NUMBER 338

NWS STORM PREDICTION CENTER NORMAN OK

550 PM CDT THU JUN 17 2010



THE NWS STORM PREDICTION CENTER HAS ISSUED A

TORNADO WATCH FOR PORTIONS OF



       NORTHEAST IOWA

       SOUTHEAST MINNESOTA

       WESTERN WISCONSIN



EFFECTIVE THIS THURSDAY AFTERNOON AND FRIDAY MORNING FROM 550 PM

UNTIL 100 AM CDT.



TORNADOES...HAIL TO 3 INCHES IN DIAMETER...THUNDERSTORM WIND

GUSTS TO 70 MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE

AREAS.



THE TORNADO WATCH AREA IS APPROXIMATELY ALONG AND 75 STATUTE

MILES EAST AND WEST OF A LINE FROM 115 MILES NORTH OF EAU CLAIRE

WISCONSIN TO 60 MILES EAST SOUTHEAST OF MASON CITY IOWA.  FOR A

COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH OUTLINE

UPDATE (WOUS64 KWNS WOU8).



REMEMBER...A TORNADO WATCH MEANS CONDITIONS ARE FAVORABLE FOR

TORNADOES AND 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.



OTHER WATCH INFORMATION...CONTINUE...WW 332...WW 333...WW

334...WW 335...WW 336...WW 337...



DISCUSSION...A FAMILY OF LONG-LIVED SUPERCELLS CONTINUE TO TRACK

GENERALLY EAST ALONG A RETREATING WARM FRONT ACROSS ERN MN ATTM.

THERE HAVE BEEN  MULTIPLE CONFIRMED TORNADOES WITH THIS ACTIVITY AND

EXPECT STORMS WILL CONTINUE TO SHIFT EAST INTO WRN WI OVER THE NEXT

FEW HOURS. SHARP INSTABILITY GRADIENT DOES EXIST AHEAD OF THE

ONGOING STORMS...ESPECIALLY NORTH AND EAST. HOWEVER...IF AIRMASS CAN

CONTINUE TO RECOVER COINCIDENT WITH THE STORM MOTION...TORNADO

POTENTIAL WILL LIKELY BE MAINTAINED FOR AWHILE LONGER.

A VERY VOLATILE AIRMASS EXISTS TO THE SOUTH AND WEST IS FEEDING THIS

CONVECTION AND AN EXPECTED INCREASE IN THE LOW LEVEL JET WOULD

SUPPORT EVENTUAL EVOLUTION INTO A QUASI-LINEAR MCS ACROSS PARTS OF

THE UPPER MIDWEST WITH TIME. THIS SCENARIO IS SUPPORTED BY SOME OF

THE LATEST HIGH RESOLUTION MODEL DATA. THUS...IN ADDITION TO

TORNADOES AND VERY LARGE HAIL...A DEVELOPING SEVERE WIND EVENT MAY

UNFOLD LATER TONIGHT.



AVIATION...TORNADOES AND A FEW SEVERE THUNDERSTORMS WITH HAIL

SURFACE AND ALOFT TO 3 INCHES. EXTREME TURBULENCE AND SURFACE

WIND GUSTS TO 60 KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO

550. MEAN STORM MOTION VECTOR 24030.





...CARBIN

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