

706 

WWUS20 KWNS 122028

SEL9

SPC WW 122028

MTZ000-130400-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 299

NWS STORM PREDICTION CENTER NORMAN OK

230 PM MDT WED JUN 12 2013



THE NWS STORM PREDICTION CENTER HAS ISSUED A



* SEVERE THUNDERSTORM WATCH FOR PORTIONS OF

  CENTRAL MONTANA



* EFFECTIVE THIS WEDNESDAY AFTERNOON AND EVENING FROM 230 PM

  UNTIL 1000 PM MDT.



* PRIMARY THREATS INCLUDE...

  SEVERAL LARGE HAIL EVENTS WITH A FEW VERY LARGE HAIL EVENTS TO 2

    INCHES IN DIAMETER POSSIBLE

  SEVERAL DAMAGING WIND GUSTS TO 70 MPH POSSIBLE



THE SEVERE THUNDERSTORM WATCH AREA IS APPROXIMATELY ALONG AND 65

STATUTE MILES EAST AND WEST OF A LINE FROM 30 MILES NORTH

NORTHWEST OF HAVRE MONTANA TO 40 MILES EAST OF DILLON MONTANA.

FOR A COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH

OUTLINE UPDATE (WOUS64 KWNS WOU9).



PRECAUTIONARY/PREPAREDNESS ACTIONS...



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 298...



DISCUSSION...STORMS ARE EXPECTED TO INCREASE AMIDST MODESTLY

UNSTABLE AIRMASS AND STRENGTHENING DEEP-LAYER FLOW THROUGH THE

EVENING HOURS. MOIST UPSLOPE FLOW REGIME IN THE LOWER LEVELS TOPPED

BY STRONGER SWLY FLOW ALOFT SHOULD CONTRIBUTE TO SUPERCELL STORM

STRUCTURES WITH PERSISTENT UPDRAFTS POSING A THREAT OF LARGE HAIL

AND DAMAGING DOWNBURST WINDS. AN ISOLATED TORNADO CANNOT BE RULED

OUT GIVEN RELATIVELY MOIST BOUNDARY LAYER AND ADEQUATE LOW LEVEL

STORM RELATIVE HELICITY SUPPORTED BY ELY COMPONENT OF THE LOW LEVEL

FLOW.



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 400. MEAN STORM

MOTION VECTOR 24030.





...CARBIN

