

997 

WWUS20 KWNS 242053

SEL8

SPC WW 242053

MTZ000-250400-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 618

NWS STORM PREDICTION CENTER NORMAN OK

245 PM MDT FRI JUL 24 2009



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       WESTERN MONTANA



EFFECTIVE THIS FRIDAY AFTERNOON AND EVENING FROM 245 PM UNTIL

1000 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 65

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

KALISPELL MONTANA TO 20 MILES SOUTHEAST OF DILLON 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 616...WW 617...



DISCUSSION...UPPER LOW OVER ERN WA WAS RESULTING IN STRONGLY

DIFFLUENT FLOW ALOFT ACROSS WRN MT. THE STORMS ARE EXPECTED TO

DEVELOP NWWD AND ALSO INTENSIFY THROUGH THE EVENING HOURS. ALTHOUGH

INSTABILITY IS NOT PARTICULARLY STRONG...MLCAPES AROUND 1000

J/KG...DEEP LAYER SHEAR NEAR 40 KT AND THE STRONG FORCING SHOULD

SUPPORT A FEW SUPERCELLS WITH THE POTENTIAL FOR LARGE HAIL AND ALSO

DAMAGING WINDS.



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 450. MEAN STORM

MOTION VECTOR 24020.





...IMY

