WATCHES: Tornado Watch Number 468

WWUS20 KWNS 121954
SEL8
SPC WW 121954
MTZ000-NDZ000-SDZ000-WYZ000-130200-

URGENT - IMMEDIATE BROADCAST REQUESTED
TORNADO WATCH NUMBER 468
NWS STORM PREDICTION CENTER NORMAN OK
150 PM MDT SUN JUN 12 2011

THE NWS STORM PREDICTION CENTER HAS ISSUED A
TORNADO WATCH FOR PORTIONS OF

SOUTHEAST MONTANA
SOUTHWEST NORTH DAKOTA
WESTERN SOUTH DAKOTA
NORTHEAST WYOMING

EFFECTIVE THIS SUNDAY AFTERNOON AND EVENING FROM 150 PM UNTIL 800
PM MDT.

TORNADOES...HAIL TO 2.5 INCHES IN DIAMETER...THUNDERSTORM WIND
GUSTS TO 70 MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE
AREAS.

THE TORNADO WATCH AREA IS APPROXIMATELY ALONG AND 90 STATUTE
MILES EAST AND WEST OF A LINE FROM 35 MILES EAST NORTHEAST OF
BAKER MONTANA TO 70 MILES SOUTH OF RAPID CITY SOUTH DAKOTA. FOR
A COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH
OUTLINE UPDATE (WOUS64 KWNS WOU8).

REMEMBER...A TORNADO WATCH MEANS CONDITIONS ARE FAVORABLE FOR
TORNADOES AND 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.

OTHER WATCH INFORMATION...CONTINUE...WW 467...

DISCUSSION...SURFACE HEATING IS REMOVING CONVECTIVE INHIBITION
ACROSS NE WY/SW SD NEAR THE SURFACE LOW AND WARM FRONT...WITH STORM
DEVELOPMENT EXPECTED BY 21-22Z. STORM DEVELOPMENT WILL BE FURTHER
SUPPORTED BY THE APPROACH OF THE PRIMARY SHORTWAVE TROUGH OVER NW
WY/S CENTRAL MT...AND A SEPARATE SPEED MAX EJECTING NEWD FROM NRN
CO. MODERATE INSTABILITY IS PRESENT IN THE WARM SECTOR /MLCAPE AOA
2000 J PER KG/...WHILE VERTICAL SHEAR IS FAVORABLE FOR SUPERCELLS
WITH LARGE HAIL. THE MORE PROBABLE AREA FOR A COUPLE OF TORNADOES
WILL BE NE WY/NW SD WHERE LOW-LEVEL SHEAR AND MOISTURE ARE MAXIMIZED
ALONG THE WARM FRONT...AND WHERE INITIALLY DISCRETE STORMS ARE
EXPECTED. LATER THIS AFTERNOON/EVENING...CONVECTION WILL LIKELY
GROW UPSCALE INTO A CLUSTER/MCS AND SPREAD NEWD WITH A CONTINUED
RISK FOR LARGE HAIL AND DAMAGING WINDS.

AVIATION...TORNADOES AND A FEW SEVERE THUNDERSTORMS WITH HAIL
SURFACE AND ALOFT TO 2.5 INCHES. EXTREME TURBULENCE AND SURFACE
WIND GUSTS TO 60 KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO
500. MEAN STORM MOTION VECTOR 23025.

...THOMPSON

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