Regional Jet 900 (CRJ900)
Flight Crew Air Transport Pilot (ATP)
Aircraft Equipment Problem Less Severe; Deviation - Altitude Excursion From Assigned Altitude; Inflight Event / Encounter Weather / Turbulence; Inflight Event / Encounter Loss Of Aircraft Control
Flight Crew Regained Aircraft Control; Flight Crew Returned To Clearance
Weather; Aircraft; Procedure
While flying at 23;000 feet 250 miles west of San Antonio; Texas while in IMC we entered a thunderstorm.  Radar was on but painted nothing.  Turbulence was severe and 3;000 feet of altitude was lost.  Had all we could do to keep control of the aircraft.  Finally left the storm with no aircraft damage noted.
During cruise flight at FL350 Center mentioned they had to descend us to FL230 due congestion and moderate turbulence. I advised the Flight Attendants of the moderate turbulence. Level at 230 Center advised if we had to deviate to keep them advised. We were IMC and nothing was painted on the radar. We flew into severe weather. Autopilot disengaged and it was difficult to focus on the instruments. We advised ATC unable to maintain altitude and reported severe turbulence.
CRJ-900 flight crew reported being descended by ATC to FL230 due to traffic and turbulence ahead. At FL230 a thunderstorm not depicted on the Radar was penetrated resulting in a severe turbulence encounter and loss of 3;000 feet before control is regained.