Incident Overview
An aircraft in cruise at FL330 experienced a sudden turbulence event while passing through a stratus layer of clouds. The fasten seat belt sign had been activated prior to the event, and passengers were briefed about the possibility of turbulence during the approach.
Turbulence Encounter
The captain reported that the airplane entered a stratus cloud layer with a small thunderstorm cell approximately 20 miles to the left of the flight path. A 'sudden jolt' was felt, followed by 10 to 12 seconds of light to occasionally moderate turbulence. The turbulence ceased after the aircraft exited the clouds, and smooth air prevailed for the rest of the flight.
Crew and Cabin Impact
A flight attendant in the aft cabin sustained a broken ankle as a result of the turbulence.
Weather Conditions
The destination airport was reporting thunderstorm activity near the airport at the time of the event.