WATCHES: Severe Thunderstorm Watch Number 453

WWUS20 KWNS 111904
SEL3
SPC WW 111904
MTZ000-SDZ000-WYZ000-120200-

URGENT - IMMEDIATE BROADCAST REQUESTED
SEVERE THUNDERSTORM WATCH NUMBER 453
NWS STORM PREDICTION CENTER NORMAN OK
105 PM MDT SUN JUL 11 2010

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

FAR SOUTHEAST MONTANA
WESTERN SOUTH DAKOTA
NORTHEAST WYOMING

EFFECTIVE THIS SUNDAY AFTERNOON AND EVENING FROM 105 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 80
STATUTE MILES EAST AND WEST OF A LINE FROM 35 MILES NORTH
NORTHEAST OF BROADUS MONTANA TO 80 MILES SOUTH SOUTHEAST OF RAPID
CITY SOUTH DAKOTA. FOR A COMPLETE DEPICTION OF THE WATCH SEE THE
ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU3).

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 450...WW 451...WW 452...

DISCUSSION...TSTMS ARE EXPECTED TO INCREASE IN COVERAGE AND
INTENSITY THIS AFTERNOON IN ADVANCE OF MIDLEVEL TROUGH PROGRESSING
ESEWD THROUGH THE NRN HIGH PLAINS. RESIDUAL BOUNDARY LAYER
DEWPOINTS IN THE 50S WITHIN POST-FRONTAL AIR MASS COUPLED WITH STEEP
LAPSE RATES WILL SERVE TO BOOST MLCAPE TO 1000-2000 J/KG THROUGH THE
REMAINDER OF THE AFTERNOON. WHILE NOT OVERLY STRONG...THE PRESENCE
OF 30-40 KT DEEP-LAYER SHEAR IN CONCERT WITH THE STEEP LAPSE RATES
AND CONVECTIVE INSTABILITY WILL SUPPORT THE DEVELOPMENT OF ORGANIZED
STORMS INCLUDING SUPERCELLS WITH THE THREAT FOR LARGE HAIL AND
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 500. MEAN STORM
MOTION VECTOR 29025.

...MEAD

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