WATCHES: Severe Thunderstorm Watch Number 578

WWUS20 KWNS 131902
SEL8
SPC WW 131902
MTZ000-WYZ000-140200-

URGENT - IMMEDIATE BROADCAST REQUESTED
SEVERE THUNDERSTORM WATCH NUMBER 578
NWS STORM PREDICTION CENTER NORMAN OK
100 PM MDT MON JUL 13 2009

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

CENTRAL AND PART OF EASTERN MONTANA
PART OF NORTH-CENTRAL WYOMING

EFFECTIVE THIS MONDAY AFTERNOON AND EVENING FROM 100 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 90
STATUTE MILES EAST AND WEST OF A LINE FROM 60 MILES SOUTH
SOUTHEAST OF BILLINGS MONTANA TO 80 MILES NORTHWEST OF GLASGOW
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 576...WW 577...

DISCUSSION...TSTMS ARE EXPECTED TO INTENSIFY AHEAD OF STRONG SHORT
WAVE TROUGH AND ASSOCIATED COLD FRONT MOVING EWD THROUGH THE NRN
HIGH PLAINS. GIVEN THE PRESENCE OF STEEP LOW TO MIDLEVEL LAPSE
RATES...MODERATE CONVECTIVE INSTABILITY AND STRENGTHENING DEEP-LAYER
SHEAR...SETUP WILL FAVOR THE DEVELOPMENT OF SUPERCELLS AND BOWING
LINE SEGMENTS WITH THE PRIMARY THREATS BEING DAMAGING WINDS AND
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 500. MEAN STORM
MOTION VECTOR 26030.

...MEAD/THOMPSON

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