B757 Undifferentiated or Other Model
Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument; Flight Crew Multiengine
Deviation - Altitude Excursion From Assigned Altitude; Deviation / Discrepancy - Procedural Clearance; Inflight Event / Encounter Loss Of Aircraft Control; Inflight Event / Encounter Weather / Turbulence
Flight Crew Regained Aircraft Control
Weather
ATC advised of SIGMET R with reports of moderate turbulence. As we approached the forecast area of turbulence we slowed to turbulence penetration speed of .78 MACH at FL360. After a few minutes of mostly moderate turbulence with significant mountain wave turbulence... we abruptly encountered approximately 10 seconds of severe turbulence resulting in simultaneous 5 to 10 degrees roll variations; +/-10 knots airspeed variations; 5 degrees pitch variations and over 1000 fpm down resulting in approximately 100 ft. below altitude. Autopilot recover aircraft to level flight. No injuries or damage noted. Reported to ATC. A few minutes following our PIREP; another aircraft report severe turbulence. Clear Air Turbulence associated with mountain wave.Suggest better forecasting. Uber conservative routing around forecast turbulence.
Air carrier Captain reported they encountered severe turbulence associated with mountain wave which caused roll variations and altitude and airspeed deviations.