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WWUS20 KWNS 302025

SEL4

SPC WW 302025

MNZ000-NEZ000-SDZ000-310300-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 634

NWS STORM PREDICTION CENTER NORMAN OK

325 PM CDT MON AUG 30 2010



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       SMALL PART OF WESTERN MINNESOTA

       MUCH OF CENTRAL NEBRASKA

       MUCH 0F EASTERN SOUTH DAKOTA



EFFECTIVE THIS MONDAY AFTERNOON AND EVENING FROM 325 PM UNTIL

1000 PM CDT.



HAIL TO 2 INCHES IN DIAMETER...THUNDERSTORM WIND GUSTS TO 80

MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE AREAS.



THE SEVERE THUNDERSTORM WATCH AREA IS APPROXIMATELY ALONG AND 65

STATUTE MILES EAST AND WEST OF A LINE FROM 55 MILES SOUTH

SOUTHEAST OF NORTH PLATTE NEBRASKA TO 55 MILES NORTHWEST OF

ORTONVILLE MINNESOTA.  FOR A COMPLETE DEPICTION OF THE WATCH SEE

THE ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU4).



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 633...



DISCUSSION...THUNDERSTORMS EXPECTED TO INCREASE IN NUMBER AND

INTENSITY ALONG WESTERN EDGE OF STRONG MOISTURE INSTABILITY GRADIENT

IN THE AXIS OF 40-50 KT LLJ.  GIVEN THE 40-50 KT OF SHEAR AND STEEP

LAPSE RATES...DAMAGING WINDS EXPECTED TO BECOME PRIMARY SEVERE

THREAT.  HOWEVER SUFFICIENT SHEAR/INSTABILITY FOR MORE DISCRETE

STORMS INCLUDING SUPERCELLS...WHICH WOULD ENHANCE RISK OF SEVERE

INCLUDING LARGE HAIL AND ISOLATED TORNADOES.



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

TO 2 INCHES. EXTREME TURBULENCE AND SURFACE WIND GUSTS TO 70

KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 550. MEAN STORM

MOTION VECTOR 22035.





...HALES

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