thought I would share this recent experience cuz it may save someone's life. Of course I have heard of mountain waves ,saw the pictures in the pilots manual, Since I live in the mid-west it was not on the top of my list of flying concerns. OK Monday flying from C77 to Winchester VA. A tail wind like none other so I climbed to 10500 and smiled 50 to 60 knots on average ,yahoo!!! off to Grandma's house we go. Smooth flying! As I approached Winchester I could see the city so I started a let down. crossed the last ridge at 6500, at least 3000 ft above the ridge. Well, all **** broke loose just as I crossed it. Bang bang 45? roll, right, left airspeed fluctuations of 50 knts. I had the runway in sight but not sure I would get there. It settled down a bit as I got further from the ridge, but far from comfortable. I landed, even experiencing wind shear on short final. I will never forget to consider the possibility of mountain waves ever again nor should you. On self debrief and do over possibilities I would have carried full altitude to short final and come down like a helicopter in the 50 knot headwind. Just something to consider.