

309 

WWUS20 KWNS 172141

SEL4

SPC WW 172141

MNZ000-NEZ000-SDZ000-180400-



URGENT - IMMEDIATE BROADCAST REQUESTED

TORNADO WATCH NUMBER 484

NWS STORM PREDICTION CENTER NORMAN OK

440 PM CDT SAT JUL 17 2010



THE NWS STORM PREDICTION CENTER HAS ISSUED A

TORNADO WATCH FOR PORTIONS OF



       SOUTHWESTERN MINNESOTA

       NORTHEASTERN NEBRASKA

       SOUTHEASTERN SOUTH DAKOTA



EFFECTIVE THIS SATURDAY AFTERNOON AND EVENING FROM 440 PM UNTIL

1100 PM CDT.



TORNADOES...HAIL TO 4 INCHES IN DIAMETER...THUNDERSTORM WIND

GUSTS TO 90 MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE

AREAS.



THE TORNADO WATCH AREA IS APPROXIMATELY ALONG AND 60 STATUTE

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

SOUTH DAKOTA TO 20 MILES SOUTH SOUTHWEST OF ONEILL NEBRASKA.  FOR

A COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH

OUTLINE UPDATE (WOUS64 KWNS WOU4).



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 483...



DISCUSSION...STRONG CAPPING INVERSION IS EXPECTED TO GRADUALLY BE

BROKEN THE NEXT HOUR OR SO...ESPECIALLY NEAR EWD MOVING COLD

FRONT...AS UPPER FORCING APPROACHES FROM THE WEST. EFFECTIVE SHEAR

AT 60 KT AND MLCAPES BETWEEN 3000-4000 J/KG ARE FAVORABLE FOR VERY

INTENSE SUPERCELLS. THE MAIN THREATS ARE EXPECTED TO BE VERY LARGE

HAIL...POSSIBLY BASEBALL TO SOFTBALL SIZED...AND VERY DAMAGING WINDS

TO 80 KT. HOWEVER...THE STRENGTH OF THE SHEAR AND INSTABILITY WOULD

ALSO SUPPORT TORNADOES.



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

SURFACE AND ALOFT TO 4 INCHES. EXTREME TURBULENCE AND SURFACE

WIND GUSTS TO 80 KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO

550. MEAN STORM MOTION VECTOR 29025.





...IMY

