Thanks for the comments! Here is a second version that I think works far better.
The clouds have not changed, but I lowered the camera way down into the trees and compacted the view to just pick up the section of clouds that I thought worked the best.
The clouds are made up of three layers. I first created a very large dark cloud which is at the highest elevation. Underneath this I added two layers of wispy warped bright gray clouds masked by the big cloud. Seemingly because of the lightness they really picked up on the light from the rising sun.
This second image took just shy of 24 hours on a slower two core system.
Vegetation includes common spruce and bushes from Lightnings free offerings and the Sweet Chestnut from
floraworks3d.comThanks for taking a look!