Even a tree line will make a rotor downwind.
A Helio courier went into Lake Isabel ( altitude ~2800ft) a few years back. From the post accident description it sounded like a rotor coming from a NW wind over a ridge line got him just after lift off.
I do know my M5-235 has failed to take off or not wanted to climb into a NW wind on Lake Isabel due to the rotor. A little longer time on the beach at a beautiful lake waiting for the conditions to improve is not a big price to pay.
Have no idea what was going on w/ the A5. I would like to hear a pilot de-brief on the accident as a teaching moment.
