

464 

WWUS20 KWNS 051941

SEL9

SPC WW 051941

MTZ000-060300-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 359

NWS STORM PREDICTION CENTER NORMAN OK

140 PM MDT TUE JUN 5 2012



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       SOUTHWEST AND CENTRAL MONTANA



EFFECTIVE THIS TUESDAY AFTERNOON AND EVENING FROM 140 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 85

STATUTE MILES EAST AND WEST OF A LINE FROM 50 MILES SOUTH OF

LIVINGSTON MONTANA TO 55 MILES NORTH OF BOZEMAN MONTANA.  FOR A

COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH OUTLINE

UPDATE (WOUS64 KWNS WOU9).



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 358...



DISCUSSION...TSTMS ARE EXPECTED TO INCREASE IN COVERAGE AND

INTENSITY THIS AFTERNOON ALONG THE HIGH TERRAIN AS LARGE-SCALE

FORCING FOR ASCENT STRENGTHENS FROM THE SW.  AMBIENT AIR MASS IS

CHARACTERIZED BY STEEP LAPSE RATES AND DEWPOINTS IN THE MID 40S-LOW

50S WITH RESULTING SBCAPE OF 500-1000 J/KG.  VERTICAL SHEAR IS ALSO

FORECAST TO STRENGTHEN MARKEDLY LATE THIS AFTERNOON INTO EVENING IN

CONJUNCTION WITH ARRIVAL OF NEGATIVELY TILTED MIDLEVEL TROUGH.  AS

SUCH...THE THREAT FOR ORGANIZED STORM MODES...INCLUDING SUPERCELLS

WILL INCREASE WITH A RISK FOR DAMAGING WINDS AND 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 450. MEAN STORM

MOTION VECTOR 17035.





...MEAD

