

295 

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

