I was out in the School Tecnam on late Monday morning for a bit over an hour from Lethbridge and on returning while entering circuit I noticed the wind had picked up a bit but was still Nth West where it was when I'd left. Probably about ten kts with gusts so a bit of cross wind from the right on rwy 28. This is fine but you have to expect a bit of turbulence on final as you cross the tree line at the highway and also just before touch down from the hangers on the right. What made this interesting was just as I was about to come over the fence having already hit some of the expected rough air there was this sudden feel of a big drop in air speed. Now I'd checked only a second before as I crossed the road 60kts, a full flap approach and then this nothingness feel. Even before I could react with throttle as I glanced at the ASI it was wildly swinging up from below 60kts to 70kts and back to 60 again where it was originally, everything then continued on as normal with a right wing low touch down and a normal roll out. I had cockpit video and so I reviewed that few seconds, unfortunately with the turbulence tossing me around a little my head got in the way of the ASI and I didn't see how low it actually went but the wild swing back up was very evident. Not one I'd felt before but then I'm only a low hours pilot, have others experienced this sort of thing? Nico.