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000 

WWUS20 KWNS 072001

SEL5

SPC WW 072001

MTZ000-SDZ000-WYZ000-080300-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 565

NWS STORM PREDICTION CENTER NORMAN OK

200 PM MDT TUE AUG 7 2007



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       SOUTHEAST MONTANA

       WESTERN SOUTH DAKOTA

       NORTHEAST WYOMING



EFFECTIVE THIS TUESDAY AFTERNOON AND EVENING FROM 200 PM UNTIL

900 PM 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 100

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

BUFFALO SOUTH DAKOTA TO 75 MILES SOUTH OF RAPID CITY SOUTH

DAKOTA.  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...STORMS ARE RAPIDLY DEVELOPING WITHIN LOW LEVEL MOISTURE

AND INSTABILITY AXIS FROM WRN SD INTO ERN WY AND SERN MT...IN

ADVANCE OF UPPER SHORT WAVE TROUGH PROGRESSING EWD TOWARD THE NRN

ROCKIES.  STEEP LAPSE RATES ASSOCIATED WITH DEEP MIXED BOUNDARY

LAYER WILL ENHANCE THREAT FOR DAMAGING WIND GUSTS...AND MLCAPE OF

1500 J/KG COUPLED WITH 30-40 KT DEEP LAYER SHEAR WILL PROMOTE

ROTATING UPDRAFTS WITH POTENTIAL FOR STRONGER CELLS TO PRODUCE LARGE

HAIL.



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 23025.





...WEISS

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