JetBlue flight 1245, a scheduled domestic passenger flight from Long Island MacArthur Airport (ISP), Islip, New York to Palm Beach International Airport (PBI), West Palm Beach, Florida, encountered turbulence during descent into PBI. As a result, one flight attendant received serious injuries. The first officer, the pilot flying, stated they entered a small cloud layer around 7,000 ft to 9,000 ft and encountered brief but sharp turbulence that lasted about 3 seconds. The flight attendants stated they had just completed their compliance checks and were securing the galley during the turbulence. One of the two aft flight attendants reported being thrown to the floor and required the assistance of the other aft flight attendant to get into their jump seat. Both aft flight attendants described the turbulence as “severe.” One of the forward flight attendants contacted the flight deck and reported to the captain that emergency medical services would be needed at the gate due to cabin crew injuries. The flight landed in PBI without further incident. The two forward flight attendants reported sustaining minor injuries. The aft flight attendant was taken to a local hospital for evaluation and was diagnosed with a fractured pelvis and vertebrae. The captain and first officer reported seeing no significant returns on the onboard weather radar at the time that turbulence was encountered. The first officer stated they reported the turbulence to air traffic control, who also advised that their radar showed no significant weather activity in that sector. There were no significant meteorological information (SIGMET), convective SIGMETs, or Center Weather Advisories over the general flight route into PBI at the time of the accident. A pilot report (PIREP) around 15:30 local time reported severe turbulence during descent into PBI at 2,000 ft, but there were no relevant PIREPs at the time flight 1245 was descending into PBI.