

509 

WWUS20 KWNS 182057

SEL2

SPC WW 182057

SDZ000-190400-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 172

NWS STORM PREDICTION CENTER NORMAN OK

255 PM MDT SAT MAY 18 2013



THE NWS STORM PREDICTION CENTER HAS ISSUED A



* SEVERE THUNDERSTORM WATCH FOR PORTIONS OF

  WESTERN SOUTH DAKOTA



* EFFECTIVE THIS SATURDAY AFTERNOON AND EVENING FROM 255 PM UNTIL

  1000 PM MDT.



* PRIMARY THREATS INCLUDE...

  SEVERAL LARGE HAIL EVENTS TO 1.5 INCHES IN DIAMETER POSSIBLE

  A FEW DAMAGING WIND GUSTS TO 60 MPH POSSIBLE



THE SEVERE THUNDERSTORM WATCH AREA IS APPROXIMATELY ALONG AND 95

STATUTE MILES EAST AND WEST OF A LINE FROM LEMMON SOUTH DAKOTA TO

75 MILES SOUTH SOUTHWEST OF PHILIP SOUTH DAKOTA.  FOR A COMPLETE

DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH OUTLINE UPDATE

(WOUS64 KWNS WOU2).



PRECAUTIONARY/PREPAREDNESS ACTIONS...



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 170...WW 171...



DISCUSSION...STORM COVERAGE IS IN THE PROCESS OF INCREASING

NEAR/NORTH AND EAST OF THE BLACK HILLS AREA...WHERE STEEP LAPSE

RATES ARE CONTRIBUTING TO A RISK FOR AT LEAST SEVERE HAIL...AIDED BY

MODEST DEEP LAYER SHEAR BENEATH 30-40 KT SOUTHERLY 500 MB FLOW.

THIS ACTIVITY LIKELY WILL PERSIST INTO THE EVENING HOURS...BEFORE

WEAKENING/SHIFTING EAST OF REGION.



AVIATION...A FEW SEVERE THUNDERSTORMS WITH HAIL SURFACE AND ALOFT

TO 1.5 INCHES. EXTREME TURBULENCE AND SURFACE WIND GUSTS TO 50

KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 450. MEAN STORM

MOTION VECTOR 24035.





...KERR

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