About 0830 eastern daylight time, on April 17, 2001, a Boeing Aircraft Company 737-200, N253UA, operated by US Airways as Flight 2686, encountered severe turbulence during climb out from Baltimore-Washington International Airport in Baltimore, Maryland. Flight 2686 was operated under the provisions of Title 14 CFR Part 121, as a scheduled, domestic passenger flight from Baltimore, Maryland, to Jacksonville, Florida. The flight departed Baltimore-Washington, Maryland, at an undetermined time. There were four crewmembers and 73 revenue passengers on board. One cabin attendant received serious injuries, and another cabin attendant received minor injuries. Undetermined weather conditions at altitude prevailed at the time of the accident. The flight operated under instrument flight rules with a flight plan filed. The flight continued to Jacksonville, Florida, without further incident. According to the pilot, no significant forecasts or pilot reports for turbulent weather were given during the preflight weather briefing by the dispatcher for his route of flight. Approximately 12-15 minutes after takeoff, at an altitude of 19,000 feet, the airplane unexpectedly encountered several areas of moderate turbulence. The "FASTEN SEAT BELT " sign was illuminated at the time of the encounter and the flight attendants were in the cabin preparing to serve the passengers. As they continued their duties, one flight attendant was thrown to the floor during an encounter. After the pilot instructed the flight attendants to take their seats, he was told that one flight attendants had sustained an ankle injury. The flight continued and landed at Jacksonville, Florida, without further incident. A review of National Weather Service information revealed that an AIRMET issued at 0945 hours forecast " occasional moderate turbulence between FL240 and FL350 associated with an upper trough. Conditions expected to continue beyond 1000 hours thru 1600 hours." The area covered in the AIRMET included Maryland and Virginia. A pilot report issued at 0736 hours over Baltimore, Maryland, by a Boeing 757 stated "moderate turbulence was encountered during the climb between 7,000 and 12,000 feet and light turbulence above. " The pilot was not informed of the 0736 pilot report.