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WWUS20 KWNS 282034

SEL6

SPC WW 282034

SDZ000-WYZ000-290400-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 696

NWS STORM PREDICTION CENTER NORMAN OK

235 PM MDT THU JUL 28 2011



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       WESTERN AND CENTRAL SOUTH DAKOTA

       EXTREME NORTHEAST WYOMING



EFFECTIVE THIS THURSDAY AFTERNOON AND EVENING FROM 235 PM UNTIL

1000 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 80

STATUTE MILES EITHER SIDE OF A LINE FROM 65 MILES SOUTH SOUTHWEST

OF BUFFALO SOUTH DAKOTA TO 70 MILES NORTH NORTHEAST 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.



OTHER WATCH INFORMATION...CONTINUE...WW 695...



DISCUSSION...STORMS ARE INCREASING FROM EXTREME NWRN SD INTO NERN WY

AS A SHORT WAVE TROUGH TRAVERSES THE AREA.  RESIDUAL MOISTURE AND

MODERATELY STEEP LAPSE RATES ARE RESULTING IN FAVORABLE INSTABILITY

WITH MLCAPE TO 1500 J/KG.  WESTERLY FLOW ALOFT AND DEEP LAYER SHEAR

OF 30-40 KT ARE EXPECTED TO ENHANCE STORM ORGANIZATION WITH ISOLATED

SUPERCELLS POSSIBLE.  CONVECTIVE COLD POOLS MAY BEGIN TO MERGE

WITHIN THE NEXT 3-4 HRS SUGGESTING POTENTIAL FOR A QLCS TO FORM AND

PROPAGATE EWD/ESEWD THROUGH THE EVENING HOURS WITH AN INCREASING

THREAT OF DAMAGING WIND GUSTS.



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 28025.





...WEISS

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