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WWUS20 KWNS 010136

SEL4

SPC WW 010136

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URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 434

NWS STORM PREDICTION CENTER NORMAN OK

735 PM MDT WED JUN 30 2010



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       WEST CENTRAL AND SOUTHWEST NORTH DAKOTA

       EXTREME NORTHWEST SOUTH DAKOTA



EFFECTIVE THIS WEDNESDAY NIGHT AND THURSDAY MORNING FROM 735 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 50

STATUTE MILES EAST AND WEST OF A LINE FROM 35 MILES SOUTHEAST OF

BUFFALO SOUTH DAKOTA TO 60 MILES NORTH OF DICKINSON NORTH DAKOTA.

 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 431...WW 432...WW 433...



DISCUSSION...STRONG/SEVERE STORMS OVER EXTREME SOUTHEAST MT HAVE

SHOWN SIGNS OF DEVELOPING NWD WITH NEW UPDRAFTS...WHILE TRAILING

STORMS TO THE WEST ARE SHOWING AN INCREASE IN CG LIGHTNING.  AIR

MASS IN ADVANCE OF THE STORMS HAS BEEN MOISTENING/DESTABILIZING WITH

SURFACE DEW POINTS IN THE UPPER 60S/LOWER 70S...CONTRIBUTING TO

MLCAPE OF 2500 J/KG.  DEEP LAYER SHEAR IS SUPPORTIVE FOR ISOLATED

SUPERCELLS /30-40 KT IN LOWEST 6 KM AGL/...AND INTENSIFYING LOW

LEVEL JET SUGGESTS SEVERE THREAT MAY SPREAD NEWD INTO TONIGHT.



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 24025.





...WEISS

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