What happened
A McDonnell Douglas DC-9-82 passenger flight encountered turbulence while descending through 15,000 feet mean sea level. Prior to entering the cloud formation, the aircraft was operating under night visual meteorological conditions. The crew observed weather radar displaying a faint green return from the cloud before the encounter. While lightning and precipitation were not observed within the cloud itself, the radar indicated a line of three or four well-defined cells on the 80-mile range. The first officer noted that the radar showed activity south of their course, with five to seven green dots displayed directly ahead on the northernmost side of the cell line. The tops of these cells were estimated to be approximately 17,000 feet MSL.
During the encounter, there was one injury involving a flight attendant who was not seated or restrained at the time of the turbulence. Although the seat belt sign had been activated, the flight attendants had not been instructed to take their seats.