

831 

WWUS20 KWNS 190201

SEL1

SPC WW 190201

IAZ000-MNZ000-WIZ000-190900-



URGENT - IMMEDIATE BROADCAST REQUESTED

TORNADO WATCH NUMBER 471

NWS STORM PREDICTION CENTER NORMAN OK

900 PM CDT THU JUN 18 2009



THE NWS STORM PREDICTION CENTER HAS ISSUED A

TORNADO WATCH FOR PORTIONS OF



       NORTHEAST IOWA

       SOUTHEAST MINNESOTA

       SOUTHWEST AND SOUTH CENTRAL WISCONSIN



EFFECTIVE THIS THURSDAY NIGHT AND FRIDAY MORNING FROM 900 PM

UNTIL 400 AM CDT.



TORNADOES...HAIL TO 2.5 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 80 STATUTE

MILES EAST AND WEST OF A LINE FROM 65 MILES NORTH OF LA CROSSE

WISCONSIN TO 50 MILES SOUTH SOUTHWEST OF LONEROCK WISCONSIN.  FOR

A COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH

OUTLINE UPDATE (WOUS64 KWNS WOU1).



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 465...WW 467...WW

468...WW 469...WW 470...



DISCUSSION...ISOLATED THUNDERSTORMS ARE BEGINNING TO DEVELOP OVER NE

IA/SW WI ALONG AN INSTABILITY GRADIENT/DIFFUSE WARM FRONT NEAR THE

MS RIVER.  DESPITE THE LOSS OF DAYTIME HEATING...STRONG INSTABILITY

REMAINS OVER THIS AREA...AND VERTICAL SHEAR IS FAVORABLE FOR

SUPERCELLS.  GIVEN THE POTENTIAL FOR CONVECTION TO BECOME ROOTED IN

THE NEAR-SURFACE LAYER WITH DEW POINTS IN THE 70S...SUPERCELLS WILL

BE CAPABLE OF PRODUCING A FEW TORNADOES AND VERY LARGE HAIL.  LATER

TONIGHT...CONVECTION COULD ALSO MOVE INTO THIS AREA FROM THE W/NW IN

THE FORM OF AN MCS WITH AN ACCOMPANYING THREAT FOR DAMAGING WINDS

AND LARGE HAIL.



AVIATION...TORNADOES AND 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

550. MEAN STORM MOTION VECTOR 28025.





...THOMPSON

