A CE750 AT FL470 ENCOUNTERED A DOWNDRAFT AND DSNDED 850 FT BEFORE GETTING CLRNC FOR A LOWER ALT BECAUSE OF CONFLICTING TFC.

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ON AUG/THU/06 WHILE FLYING FROM ZZZ1 TO ZZZ2 AND APPROX 1/2 WAY BTWN MEM AND ARG VORTAC AT FL470; WE WERE ABOVE CLOUD TOPS IN CLR AIR. WE HAD DEVIATED L OF COURSE TO AVOID WX AND WERE NOW FLYING ON A HDG OF 270 DEGS MAGNETIC. INITIALLY WE ENCOUNTERED SOME UNSTABLE AIR WITH UPDRAFTS BUT SUDDENLY DOWNDRAFTS WERE ENCOUNTERED ALONG WITH WARMER TEMPS. IT WAS OBVIOUS THAT WE WOULD NEED A LOWER ALT SINCE AIRSPD WAS DETERIORATING. ATC ADVISED LOWER WAS NOT AVAILABLE DUE TO TFC AT FL450. WE THEN REQUESTED AN IMMEDIATE TURN WITH LOWER ALT. A TURN TO 180 DEGS WAS ISSUED WITH LOWER ALT PERMISSIBLE WHEN HDG 180 DEGS. AT THAT MOMENT I DISENGAGED THE AUTOPLT AS AN AIRFRAME BUFFET BEGAN. I STARTED TURNING AND DSNDING TO MAINTAIN ACFT CTL AND AIRSPD. BY THE TIME I REACHED 180 DEGS; I HAD LOST 850 FT AND ALTIMETER WAS READING 46150 FT. WE THEN WERE ABLE TO DSND TO FL430 AT NORMAL AIRSPD AND TURN BACK ON COURSE. THE REMAINDER OF THE FLT WAS NORMAL AND UNEVENTFUL. THE OTHER ACFT WAS ASKED TO TURN 30 DEGS L AT THE TIME WE BEGAN OUR L TURN AND DSCNT. I WILL CERTAINLY GIVE TSTMS AN EVEN WIDER BERTH IN THE FUTURE!