WE HADN'T THE FOGGIEST

Ever been out on the dance floor cutting a rug and then hear the fiddlers suddenly change their tune? It can be awkward, especially in the midst of a do-si-do.

We were in wave about a mile above the clouds when we noticed the lift weakening, cloud thickening, and our wave's crest creeping forward, upwind. (Clouds ordinarily shrink when lift weakens, and waves that migrate almost always move downwind.) This anomaly made us look closer and think more carefully, at which point the fun began.

Before, there'd been just one layer of broken cloud between us and the earth, and ample avenues for descent. But in pointing out that a second layer had formed above it I spied a third layer hiding beneath it. A more greenish shade... The signature of ground fog!

At once the sole mission was to find how quickly we could get DOWN. Even diving with full spoilers, we had several huge spirals to better observe and understand what was happening. Our wave wind had been from the south, but while we faced that direction very different weather was encroaching from the north, behind us. As our wave flattened out converging winds generated broad uplift almost everywhere, collectling clouds into a deepening mass. Safe escape routes were looking trickier by the moment.

We had to fly away some distance for a neat passage back to the airport, and got there barely in time. Fog was rolling up the the runway before we finished securing our bird! A few minutes later it rained.

No clouds up there today, but I've now experienced this same kind of rapid sea change at three different soaring sites, so the question is not if, but when and where it will occur again...