I've seen a couple people pull this off. I watched my friend Dawn do it on Virginia's Skyline Drive many times in succession. On the start of the downhills, she'd pull her jacket out, casually put it on, zip it up (while steering with her knees through the turns) and then when the road would tilt up, she'd casually take it off, roll it up, stuff it in her pocket, and continue on. I was in awe.