

000 

WWUS20 KWNS 252001

SEL5

SPC WW 252001

IAZ000-MNZ000-WIZ000-260300-



URGENT - IMMEDIATE BROADCAST REQUESTED

TORNADO WATCH NUMBER 75

NWS STORM PREDICTION CENTER NORMAN OK

255 PM CDT SUN MAR 25 2007



THE NWS STORM PREDICTION CENTER HAS ISSUED A

TORNADO WATCH FOR PORTIONS OF



       NORTHEAST IOWA

       EAST CENTRAL AND SOUTHEAST MINNESOTA

       WEST CENTRAL AND SOUTHWEST WISCONSIN



EFFECTIVE THIS SUNDAY AFTERNOON AND EVENING FROM 255 PM UNTIL

1000 PM CDT.



TORNADOES...HAIL TO 2 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 85 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 WOU5).



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.



DISCUSSION...A MID LEVEL TROUGH CONTINUES TO MOVE EWD OVER W/SW

MN...WHILE SURFACE HEATING/DESTABILIZATION HAS PROGRESSED THROUGH

THE AFTERNOON IN THE WARM SECTOR IN ADVANCE OF THIS SYSTEM.  IT

APPEARS THAT CONVECTIVE INHIBITION IS WEAKENING AND THUNDERSTORM

INITIATION IS EXPECTED BY 21-22Z ALONG A SURFACE TROUGH ACROSS NRN

IA INTO SRN MN.  SURFACE TEMPERATURES IN THE MID-UPPER 70S AND

DEWPOINTS IN THE MID-UPPER 50S ARE CONTRIBUTING TO MLCAPE VALUES

APPROACHING 1000 J/KG...AND LOCAL PROFILERS/VWPS SHOW FAVORABLE

VERTICAL SHEAR FOR SUPERCELLS.  THE INITIAL CONVECTION SHOULD TAKE

THE FORM OF DISCRETE SUPERCELLS CAPABLE OF PRODUCING LARGE HAIL AND

DAMAGING WINDS...THOUGH CONVECTION MAY GROW INTO A MORE LINEAR MCS

BY LATE EVENING INTO WI.  RELATIVELY LARGE TEMPERATURE-DEWPOINT

SPREADS COULD TEMPER THE TORNADO THREAT SOMEWHAT INITIALLY...BUT THE

ENVIRONMENT STILL APPEARS SUPPORTIVE OF A FEW TORNADOES NEAR AND E

OF THE MS RIVER LATE THIS AFTERNOON INTO THIS EVENING.



AVIATION...TORNADOES AND 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

450. MEAN STORM MOTION VECTOR 24045.





...THOMPSON

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