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WWUS20 KWNS 232025

SEL5

SPC WW 232025

NDZ000-NEZ000-SDZ000-240400-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 685

NWS STORM PREDICTION CENTER NORMAN OK

325 PM CDT SUN SEP 23 2007



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       PARTS OF CENTRAL NORTH DAKOTA

       MUCH OF WESTERN NEBRASKA

       MUCH OF CENTRAL AND PARTS OF WESTERN SOUTH DAKOTA



EFFECTIVE THIS SUNDAY AFTERNOON AND EVENING FROM 325 PM UNTIL

1100 PM CDT.



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 85

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

BISMARCK NORTH DAKOTA TO 65 MILES SOUTH OF MULLEN NEBRASKA.  FOR

A COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH

OUTLINE UPDATE (WOUS64 KWNS WOU5).



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.



DISCUSSION...STRONG COLD FRONT CURRENTLY MOVING INTO WRN SD/NEB

PANHANDLE WILL INITIATE STRONG/SEVERE THUNDERSTORMS AS IT ENCOUNTERS

AN UNSTABLE DEEPLY MIXED AIR MASS.  STRONG DEEP LAYER SHEAR AHEAD OF

EJECTING TROUGH FROM THE ROCKIES WILL ENHANCE ALONG WITH STEEP LOW

LEVEL LAPSE RATES...DAMAGING WIND POTENTIAL AS STORMS MOVE/DEVELOP

RAPIDLY NE/NNEWD THRU THE EVENING.



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 21035.





...HALES

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