We left Chambery, having planned the “out” route. The first leg, was to re-trace our track into the Alps.
Cloud base was c5,000 ft as we headed past the lake. By the time we had cleared Chambery air space and crossed the lake to our valley route out, cloud base was 3,500ft. Still plenty. We flew up the valley observing the clouds clinging to the western side mountains. We cleared the first set of HT cables.
In the lead, I spotted the second set, but as the valley narrowed, the clinging clouds spread across the entire valley and I was only just able to fly over them. With 4 miles to the exit, cloud base dropped to 1,200ft and we considered options. I called up Ambrieu, thinking I needed to land and was glad to see their runway. Then, as quickly as it had appeared, the clouds dispersed and we continued on to our first scheduled stop at Chalon.