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WWUS20 KWNS 311918

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URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 554

NWS STORM PREDICTION CENTER NORMAN OK

120 PM MDT SAT JUL 31 2010



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       LARGE PART OF SOUTHWEST AND CENTRAL MONTANA



EFFECTIVE THIS SATURDAY AFTERNOON AND EVENING FROM 120 PM UNTIL

800 PM MDT.



HAIL TO 1.5 INCHES IN DIAMETER...THUNDERSTORM WIND GUSTS TO 75

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



THE SEVERE THUNDERSTORM WATCH AREA IS APPROXIMATELY ALONG AND 100

STATUTE MILES EITHER SIDE OF A LINE FROM 30 MILES SOUTHWEST OF

DILLON MONTANA TO 75 MILES EAST SOUTHEAST OF HAVRE MONTANA.  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 552...WW 553...



DISCUSSION...THUNDERSTORMS ARE INCREASING ACROSS SWRN MT AHEAD OF

TROUGH AND MID LEVEL WIND MAX.  WITH STEEP LAPSE RATES AND MLCAPES

TO 1000 J/KG ACROSS THE WATCH...STORMS WILL INTENSIFY FURTHER

ENHANCING PARTICULARLY THE WIND DAMAGE THREAT.  PRIMARY WIND DAMAGE

CONCERN WILL BE WITH LINE/BOW STRUCTURES THAT DEVELOP.



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

TO 1.5 INCHES. EXTREME TURBULENCE AND SURFACE WIND GUSTS TO 65

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

MOTION VECTOR 24035.





...HALES

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