>>1886877I don't have PS so I can only approximate the required effects.
You have a solid background of the darkest shade.
With a "cloud" airbrush, set to the lightest shade and mostly transparent,
build up the overall shape you need, then apply a lot of Gaussian blur.
You may have to blur in sections to avoid edge-effects.
I couldn't make those square shapes, so I added a "snow" effect on another layer and reduced its opacity.
Does this look reasonably close?