

031 

WWUS20 KWNS 162117

SEL5

SPC WW 162117

SDZ000-170200-



URGENT - IMMEDIATE BROADCAST REQUESTED

TORNADO WATCH NUMBER 435

NWS STORM PREDICTION CENTER NORMAN OK

420 PM CDT TUE JUN 16 2009



THE NWS STORM PREDICTION CENTER HAS ISSUED A

TORNADO WATCH FOR PORTIONS OF



       SOUTHEAST SOUTH DAKOTA



EFFECTIVE THIS TUESDAY AFTERNOON AND EVENING FROM 420 PM UNTIL

900 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 55 STATUTE

MILES EAST AND WEST OF A LINE FROM 20 MILES NORTH NORTHWEST OF

HURON SOUTH DAKOTA TO 50 MILES SOUTH OF MITCHELL SOUTH DAKOTA.

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.



OTHER WATCH INFORMATION...CONTINUE...WW 433...WW 434...



DISCUSSION...SUPERCELLS WILL CONTINUE TO MOVE/DEVELOP SSEWD ALONG A

STALLED BAROCLINIC ZONE ACROSS SE SD...ALONG THE SERN PERIPHERY OF A

MID LEVEL LOW NEAR THE ND/SD BORDER.  DEEP LAYER AND LOW-LEVEL SHEAR

ARE SUFFICIENT FOR SUPERCELLS ALONG THE INSTABILITY AXIS NEAR AND E

OF THE BOUNDARY...WHILE LOW-LEVEL VERTICAL VORTICITY IS ALSO

MAXIMIZED ALONG THE WIND SHIFT.  A FEW TORNADOES...LARGE HAIL...AND

ISOLATED DOWNBURST WINDS WILL BE POSSIBLE FOR THE NEXT FEW HOURS.



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

500. MEAN STORM MOTION VECTOR 32015.





...THOMPSON

