WATCHES: Severe Thunderstorm Watch Number 447

WWUS20 KWNS 101934
SEL7
SPC WW 101934
SDZ000-110300-

URGENT - IMMEDIATE BROADCAST REQUESTED
SEVERE THUNDERSTORM WATCH NUMBER 447
NWS STORM PREDICTION CENTER NORMAN OK
230 PM CDT SAT JUL 10 2010

THE NWS STORM PREDICTION CENTER HAS ISSUED A
SEVERE THUNDERSTORM WATCH FOR PORTIONS OF

CENTRAL AND PART OF EASTERN SOUTH DAKOTA

EFFECTIVE THIS SATURDAY AFTERNOON AND EVENING FROM 230 PM UNTIL
1000 PM CDT.

HAIL TO 2.5 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 70
STATUTE MILES EAST AND WEST OF A LINE FROM 35 MILES NORTH
NORTHWEST OF ABERDEEN SOUTH DAKOTA TO 75 MILES SOUTHWEST OF
CHAMBERLAIN SOUTH DAKOTA. FOR A COMPLETE DEPICTION OF THE WATCH
SEE THE ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU7).

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 446...

DISCUSSION...HOT AND HUMID CONDITIONS AHEAD OF WEAK SURFACE LOW /W
OF ABR/ AND ATTENDANT PRESSURE TROUGH HAVE LED TO A STRONGLY
UNSTABLE AIR MASS THIS AFTERNOON WITH MLCAPE OF 3000-4000 J/KG.
SUBSIDENCE IN THE WAKE OF INITIAL SHORT WAVE TROUGH NOW OVER MN HAS
INHIBITED SURFACE-BASED TSTM DEVELOPMENT ACROSS THE WARM SECTOR THUS
FAR. HOWEVER...THE INCREASING INFLUENCE OF AN UPSTREAM SHORT WAVE
TROUGH MOVING INTO WRN SD SHOULD CONTRIBUTE TO ISOLATED TO SCATTERED
TSTM DEVELOPMENT BY LATE AFTERNOON. AREA PROFILER AND VWP DATA
INDICATE THAT THE MID AND HIGH-LEVEL WIND FIELD REMAINS GENERALLY
LESS THAN 30-35 KT. HOWEVER...VERTICAL WIND PROFILES DO EXHIBIT
VEERING WINDS WITH HEIGHT WITH 30-35 KT OF DEEP-LAYER SHEAR. AS
SUCH...ENVIRONMENT WILL FAVOR STRONG/ORGANIZED STORMS INCLUDING
SUPERCELLS. WHILE A TORNADO IS POSSIBLE...IT APPEARS THAT LARGE
HAIL AND DAMAGING WIND GUSTS WILL BE THE PRIMARY HAZARDS.

AVIATION...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 600. MEAN STORM
MOTION VECTOR 28020.

...MEAD

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