

046 

WWUS20 KWNS 131557

SEL6

SPC WW 131557

NDZ000-SDZ000-132200-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 576

NWS STORM PREDICTION CENTER NORMAN OK

1000 AM MDT MON JUL 13 2009



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       SOUTHWEST NORTH DAKOTA

       CENTRAL SOUTH DAKOTA



EFFECTIVE THIS MONDAY MORNING AND AFTERNOON FROM 1000 AM UNTIL

400 PM MDT.



HAIL TO 2 INCHES IN DIAMETER...THUNDERSTORM WIND GUSTS TO 70

MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE AREAS.



THE SEVERE THUNDERSTORM WATCH AREA IS APPROXIMATELY ALONG AND 60

STATUTE MILES EAST AND WEST OF A LINE FROM 70 MILES NORTH

NORTHEAST OF LEMMON SOUTH DAKOTA TO 40 MILES WEST OF CHAMBERLAIN

SOUTH DAKOTA.  FOR A COMPLETE DEPICTION OF THE WATCH SEE THE

ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU6).



REMEMBER...A SEVERE THUNDERSTORM WATCH MEANS CONDITIONS ARE

FAVORABLE FOR 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. SEVERE THUNDERSTORMS CAN AND OCCASIONALLY

DO PRODUCE TORNADOES.



DISCUSSION...THREAT FOR ELEVATED SUPERCELLS CAPABLE OF PRODUCING

LARGE HAIL WILL PERSIST INTO THE AFTERNOON ALONG AND JUST NE OF THE

WARM FRONT IN ND/SD...WHERE LOW-LEVEL WAA AND ASCENT ARE FOCUSED IN

ADVANCE OF A WEAK LEAD SHORTWAVE TROUGH.  BY MID AFTERNOON...THE WRN

PORTIONS OF THE WATCH AREA WILL LIKELY BE REPLACED WITH A TORNADO

WATCH TO REFLECT AN INCREASING TORNADO THREAT AS THE WARM FRONT

LIFTS SLOWLY NEWD AND THE BOUNDARY LAYER DESTABILIZES.



AVIATION...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 31020.





...THOMPSON

