Richard, Diane,
Greetings. Happened to see this while thinking about headroom. There is some detail in the jpeg...
I used Silver Efex Pro to convert to monochrome, used the detailing tools (structure) to bring out the edge detail in the whites and whites contrast to bring them out more. Blended back color with luminosity blend (Photoshop) and masked to blend just the snow back to the original (Photoshop). A similar sort of thing could be done with a monochrome conversion in PS then precise curves adjustments to add contrast to the whites instead of the SEP step.
I imagine there is even more headroom using RAW conversion as Diane suggests. But maybe there is just enough detail in the jpeg info if enhanced.
Otherwise, the color and feather detail in this image rocks. Good show!
Cheers,
-Michael-