

479 

WWUS20 KWNS 172337

SEL8

SPC WW 172337

NEZ000-SDZ000-180700-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 448

NWS STORM PREDICTION CENTER NORMAN OK

535 PM MDT WED JUN 17 2009



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       PARTS OF NORTHWEST NEBRASKA

       MUCH OF WESTERN AND CENTRAL SOUTH DAKOTA



EFFECTIVE THIS WEDNESDAY AFTERNOON AND THURSDAY MORNING FROM 535

PM UNTIL 100 AM 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 110

STATUTE MILES NORTH AND SOUTH OF A LINE FROM 50 MILES WEST

SOUTHWEST OF RAPID CITY SOUTH DAKOTA TO 35 MILES EAST SOUTHEAST

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

SEE THE ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU8).



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.



OTHER WATCH INFORMATION...CONTINUE...WW 439...WW 440...WW

441...WW 442...WW 443...WW 445...WW 444...WW 446...WW 447...



DISCUSSION...STORMS CONTINUE TO INCREASE ACROSS THE WW AREA AHEAD OF

A MID-LEVEL SHORT-WAVE TROUGH EJECTING NEWD FROM THE CENTRAL

ROCKIES.  SOMEWHAT MODEST INSTABILITY /500 TO 1000 J/KG MIXED-LAYER

CAPE/ EXISTS ACROSS THIS AREA...BUT WITH THE NRN FRINGE OF STRONGER

WSWLY MID-LEVEL FLOW EXTENDING ACROSS THIS REGION...STORMS

DEVELOPING IN CONJUNCTION WITH THE EJECTING UPPER FEATURE SHOULD

REMAIN LOCALLY-ORGANIZED -- AND CAPABLE OF PRODUCING HAIL AND

LOCALLY-DAMAGING WINDS.



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 450. MEAN STORM

MOTION VECTOR 24035.





...GOSS

