First I selected the sky and set it aside as a separate layer and applied Nik Detail Extractor to it at about 50% to recover detail in clouds.
On the base layer I used Nik Color Contrast Range filter to improve the contrast and also make the interplay between sunlit and non-sunlit areas more interesting and dynamic.

I may try cloning out the large tree on the left, but that's another project for the next few days.