RPTR SAYS HE WAS PUSHED INTO THE PCA BY UPDRAFTS AND CLOUDS.

Narrative

I WAS FLYING VFR ON TOP OF THE OVCST (ON COURSE) N TO SEATTLE; WA; WHEN I ENTERED CONTINENTAL AIRSPACE. THE CLOUDS (TOPS) WERE AT 12000-14000 FT AND AT THE TIME OF THE INCIDENT UPDRAFTS AND CLOUDS PUSHED ME UP INTO THE CTLED AIRSPACE. I WAS ON RADAR FOLLOWING TO SEATTLE ATC CTLR. THE CTLR ADVISED ME I HAD ENTERED RESTR AIRSPACE IN WHICH I REQUESTED A TURN TO THE W TO SEE IF I COULD DSND WITHOUT ENTERING THE CLOUDS. THIS WAS NOT POSSIBLE. I THEN REQUESTED A TURN TO THE E AND FOUND THE TOPS OF CLOUDS BUILDING EVEN HIGHER. SEVERAL TIMES ATC REQUESTED I DSND AND I STATED I DID NOT WANT TO ENTER THE CLOUDS. ANOTHER ACFT HAD DECLARED AN EMER AND WAS IN THE CLOUDS ICING UP AND WISHED VECTORING TO THE NEAREST ARPT. AT THAT TIME; I INFORMED ATC I WAS TURNING BACK AND REQUESTED AN ARPT (REDMOND; OR) WHERE THE OVCST WAS BROKEN. I DSNDED WITHOUT INCIDENT. FACTORS THAT WERE CRITICAL IN MY DECISIONS WERE: NOT TO ENTER THE CLOUDS IFR IN KNOWN ICING. NOT TO ENTER THE CLOUDS IFR IN KNOWN SNOW. NOT TO ENTER THE CLOUDS IFR IN KNOWN TURB. ABOVE THE CLOUDS I HAD VISUAL REF AND CTL. ONE ACFT IN THE CLOUDS DECLARED AN EMER. NOT IFR RATED PLT TO FLY IN IFR CONDITIONS. THE SAFE THING FOR ME TO DO WAS TO REMAIN ON TOP AND RETURN TO A CLR ARPT WITH RADAR FOLLOWING AND VECTORS. FUTURE PREVENTION WOULD BE NOT TO FLY INTO BUILDING CLOUD FORMATIONS; AND TO ALLOW ADEQUATE SPACE BTWN ACFT AND TOPS AND CARRY ADDITIONAL OXYGEN SINCE I WAS LOW BUT HAD ENOUGH FOR THE TRIP.