lovely mood!
mind telling how did you approach snow on trees?
I have duplicated the polygons of the pine needles and positioned an centimeter above. Then I added a snow material with a displacement map. The texture is an long oval with soft edge, so it looks like as if a heap of snow is on the needles. This looks good however only from far away well out (like the forest behind) ;-)
Hmmmmm I'm having a hard time reconciling that the sky you added in post doesn't match the lighting in the scene
The HDRI was properly positioned. The sun in the HDRI stood exactly at this point. I have later aligned the backplate picture on this position.