Aircraft and Flight Details
A Boeing 727-200 was in cruise at Flight Level 350 when it encountered severe turbulence associated with a line of thunderstorms. The turbulence was forecast, and a convective SIGMET was in effect for the route of flight, calling for thunderstorms 15 miles wide with tops reaching Flight Level 450.
Turbulence Encounter
Prior to the severe turbulence, the captain had turned on the seat belt sign after the aircraft experienced some light chop. All passengers and flight attendants were seated. Cabin service was nearly completed. As severe turbulence began, a flight attendant got up to stow a beverage cart in the aft galley. The severe turbulence lasted for approximately 60 seconds.
Weather Conditions
The line of thunderstorms was forecast to be 15 miles wide, with cloud tops reaching Flight Level 450. The convective SIGMET indicated the presence of these conditions along the aircraft's route.
Cabin Service Actions
The captain did not direct the flight attendants to secure the cabin or discontinue service before the severe turbulence was encountered. The flight attendant who stood to stow the beverage cart was doing so when the turbulence intensified.