

707 

WWUS20 KWNS 062306

SEL7

SPC WW 062306

MTZ000-WYZ000-070400-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 557

NWS STORM PREDICTION CENTER NORMAN OK

500 PM MDT MON JUL 6 2009



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       SOUTHEASTERN MONTANA

       NORTHEASTERN WYOMING



EFFECTIVE THIS MONDAY AFTERNOON AND EVENING FROM 500 PM UNTIL

1000 PM MDT.



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 70

STATUTE MILES EITHER SIDE OF A LINE FROM 60 MILES SOUTH OF

GILLETTE WYOMING TO 30 MILES NORTH NORTHEAST OF MILES CITY

MONTANA.  FOR A COMPLETE DEPICTION OF THE WATCH SEE THE

ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU7).



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 553...WW 554...WW

555...WW 556...



DISCUSSION...LINE OF DEVELOPING STORMS...ASSOCIATED WITH AN UPPER

LEVEL IMPULSE...IS EXPECTED TO MOVE ENEWD AT 35 KT THROUGH PORTIONS

OF SERN MT/NERN WY DURING THE EVENING HOURS. A WARM FRONT WAS

LOCATED NEAR THE WY/MT BORDER...WITH ELY BOUNDARY LAYER WINDS AND

MODERATE INSTABILITY FAVORABLE FOR A FORWARD-PROPAGATING MCS ACROSS

SERN MT. DESPITE WEAKER DEEP LAYER SHEAR IN NERN WY...THE ORGANIZED

OUTFLOW AND 25-30 DEGREE TEMPERATURE/DEWPOINT SPREADS WILL ALSO

SUPPORT STRONG TO SEVERE WIND GUSTS.



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 450. MEAN STORM

MOTION VECTOR 25035.





...IMY

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