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URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 582

NWS STORM PREDICTION CENTER NORMAN OK

555 PM MDT FRI AUG 6 2010



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       SOUTHWEST NORTH DAKOTA

       WESTERN AND CENTRAL SOUTH DAKOTA



EFFECTIVE THIS FRIDAY AFTERNOON AND SATURDAY MORNING FROM 555 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 75

STATUTE MILES EAST AND WEST OF A LINE FROM 45 MILES NORTH

NORTHWEST OF LEMMON SOUTH DAKOTA TO 30 MILES EAST SOUTHEAST OF

RAPID CITY SOUTH DAKOTA.  FOR A COMPLETE DEPICTION OF THE WATCH

SEE THE ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU2).



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 579...WW 580...WW 581...



DISCUSSION...QUASI-LINEAR TSTM CLUSTER NOW ENTERING WRN SD EXPECTED

TO CONTINUE GENERALLY E/ESE...AS NEW DEVELOPMENT OCCURS

PREFERENTIALLY ALONG LOW LVL MOISTURE/INSTABILITY AXIS ALONG AND SW

OF WEAK NW/SE WARM FRONT.  STORMS MAY BE ASSISTED BY WEAK UPR

IMPULSE MOVING E FROM NE WY...AND BY EXPECTED SLIGHT STRENGTHENING

OF SLY LLJ AFTER DARK.  WHILE COMBINATION OF SLIGHTLY-BACKED LOW LVL

FLOW AND MORE MOIST AIR NEAR FRONT COULD YIELD A TORNADO OR TWO

GIVEN DISCRETE OR SEMI-DISCRETE STORMS...LIMITED STRENGTH OF LOW LVL

SHEAR AND QUASI-LINEAR STORM MODE ALREADY ESTABLISHED /INCLUDING

CONSIDERABLE LOW LVL STORM OUTFLOW ALREADY PRESENT/...SUGGEST THAT

ANY SUCH RISK WILL REMAIN BRIEF.



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 550. MEAN STORM

MOTION VECTOR 27030.





...CORFIDI

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