A BE36 PVT PLT SUFFERS A TEMPORARY LOSS OF ACFT CTL AS THE ACFT EXECUTES AN ALT EXCURSION IN A MOUNTAIN WAVE ENCOUNTER.

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ON OCT/XX/97; I WAS ON A BUSINESS-RELATED FLT FROM 00V TO 022 ON V244 APPROX 50 MI W OF MTJ. MY ASSIGNED ALT WAS 16000 FT. JUST PRIOR TO THE OCCURRENCE; I WAS IN CLR SUNSHINE APCHING A DENSE FRONT OF CLOUDS WITH MOUNTAIN OBSCURATION AND TOPS APPEARING TO BE APPROX 20000 FT. UPON ENTERING THE CLOUDS; I IMMEDIATELY ENCOUNTERED MODERATE TO SEVERE TURB AND MODERATE RIME ICING. THE AIRPLANE'S AUTOPLT WAS ALREADY ENGAGED AND HOLDING THE AIRPLANE AT 16000 FT. I REQUESTED HIGHER ALT DUE TO RIME ICING TWICE; BUT GOT NO ANSWER. ON THE THIRD CALL; I WAS ANSWERED BY THE CTLR. I DISCONNECTED THE AUTOPLT BECAUSE MY AIRSPD AT TIMES EXCEEDED VA (DESIGN MANEUVERING SPD) AND AS I WAS SPEAKING TO THE CTLR; I WAS LIFTED BY AN UPDRAFT AT OVER 2000 FPM UNTIL REACHING 17400 FT. AFTER REGAINING CTL OF THE AIRPLANE; I REQUESTED FL180. THE CTLR STATED THAT IT WAS PROBABLY UNUSABLE AND CLRED ME TO 17000 FT. THE CTLR APPARENTLY HAD ONCOMING TFC (A KING AIR) WHICH WAS GIVEN A NEW HEADING TO FLY. THERE WAS NOTHING UNUSUAL ON THE REMAINDER OF THE FLT.