As I stood waiting for a tow, I noticed that the high ceiling moving in from the Southwest had its leading edge directly overhead. It was supposed to bring in rain much later this coming evening. Getting a late start at 1:43 PM, I decided to take a 4k ft tow and make an expected glide back down to earth and land long to put the ship away. Taking off to the North, the tow plane climbed out and turned southwest under the high ceiling. I called to the pilot to make a 180 in order to fly toward the leading edge of this cover and hopefully get into some sunlight. But the 4k ft tow didn't quite make the sunlight, so I released just under the edge of this high ceiling. To my surprise, the smooth air I encountered at release was lifting the Genesis at half a knot. So I searched the immediate area to find the spot of maximum lift in this very smooth, wave like air. At the point of maximum lift, which was about 2 knots, I recorded its position by pressing the "mark this thermal" button on my Cambridge GPS. As the lift dropped off, I noticed that the high ceiling had moved further north. Proceeding north, the lift was found again, so I again recorded its position. I did this, repeatedly, for about an hour while gaining almost a thousand feet. I believe this lift was caused by the shear effect of the leading edge of this airmass as it moved north. I probably could have followed it further north, but decided after an hour to return to Sterling to see if there was any thermal activity down low under this cloud cover. As expected, some lift was found at 2.5 k ft msl, over the stone quarry which was still warm from the heating it had received earlier in the day. When the lift could no longer keep me aloft at 1.8 k ft, I came in for a landing to end this Sunday surprise, 1.5 hours under full cloud cover.
Bob