Narrative:

On aug/thu/06 while flying from ZZZ1 to ZZZ2 and approximately 1/2 way between mem and arg VORTAC at FL470; we were above cloud tops in clear air. We had deviated left of course to avoid WX and were now flying on a heading of 270 degrees magnetic. Initially we encountered some unstable air with updrafts but suddenly downdrafts were encountered along with warmer temperatures. It was obvious that we would need a lower altitude since airspeed was deteriorating. ATC advised lower was not available due to traffic at FL450. We then requested an immediate turn with lower altitude. A turn to 180 degrees was issued with lower altitude permissible when heading 180 degrees. At that moment I disengaged the autoplt as an airframe buffet began. I started turning and descending to maintain aircraft control and airspeed. By the time I reached 180 degrees; I had lost 850 ft and altimeter was reading 46150 ft. We then were able to descend to FL430 at normal airspeed and turn back on course. The remainder of the flight was normal and uneventful. The other aircraft was asked to turn 30 degrees left at the time we began our left turn and descent. I will certainly give thunderstorms an even wider berth in the future!

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Original NASA ASRS Text

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

Narrative: 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!

Data retrieved from NASA's ASRS site as of January 2009 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.