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858 

WWUS20 KWNS 131902

SEL8

SPC WW 131902

MTZ000-WYZ000-140200-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 578

NWS STORM PREDICTION CENTER NORMAN OK

100 PM MDT MON JUL 13 2009



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       CENTRAL AND PART OF EASTERN MONTANA

       PART OF NORTH-CENTRAL WYOMING



EFFECTIVE THIS MONDAY AFTERNOON AND EVENING FROM 100 PM UNTIL 800

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 90

STATUTE MILES EAST AND WEST OF A LINE FROM 60 MILES SOUTH

SOUTHEAST OF BILLINGS MONTANA TO 80 MILES NORTHWEST OF GLASGOW

MONTANA.  FOR A COMPLETE DEPICTION OF THE WATCH SEE THE

ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU8).



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 576...WW 577...



DISCUSSION...TSTMS ARE EXPECTED TO INTENSIFY AHEAD OF STRONG SHORT

WAVE TROUGH AND ASSOCIATED COLD FRONT MOVING EWD THROUGH THE NRN

HIGH PLAINS.  GIVEN THE PRESENCE OF STEEP LOW TO MIDLEVEL LAPSE

RATES...MODERATE CONVECTIVE INSTABILITY AND STRENGTHENING DEEP-LAYER

SHEAR...SETUP WILL FAVOR THE DEVELOPMENT OF SUPERCELLS AND BOWING

LINE SEGMENTS WITH THE PRIMARY THREATS BEING DAMAGING WINDS AND

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 500. MEAN STORM

MOTION VECTOR 26030.





...MEAD/THOMPSON

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