WATCHES: Severe Thunderstorm Watch Number 634

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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