A320
Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 200; Flight Crew Total 11624; Flight Crew Type 4970
Deviation - Altitude Excursion From Assigned Altitude; Deviation - Speed All Types; Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter Weather / Turbulence
Flight Crew Became Reoriented
Weather
At FL340; aircraft encountered moderate to severe mountain wave which brought the aircraft unexpectedly to gaining about 12 knots airspeed within seconds of the encounter which brought the aircraft five knots into the red region on the speed tape. Recovered the aircraft by turning off the autopilot; increased altitude 120 feet high and throttles to idle. Brought the aircraft back to FL340 and placed automation of aircraft back on line. Received a call from the back stating that the two flight attendants fell to the floor (not in their seats) and a customer sat down on the floor while not in her seat either. After the flight; the flight attendants said they were alright; but asked them to file a report. Wrote up the aircraft overspeed and notified maintenance.
[Report narrative contained no additional information.]
A320 flight crew reported moderate to severe mountain wave over the Sierra Nevada mountain range which caused an overspeed.