Originally Posted by
IO540
I think a crude rule is to fly 1000ft above ridges for every 10kt of wind aloft, for any downdraughts to be smaller than 500fpm.
Uhm... might work most of the times, but I was in a glider with light wind (10-15 kt) above 10000ft and good spring thermals.
The interaction between high-level wind and thermals created an unusual wave condition with climbs up to 2000 fpm at 16000 ft and sinks down to -1500 fpm nearby (but absolutely no turbulence).
Cumulus elongaten in lenticular clouds up to (estimated) 22000 ft.