Using Blender (2.90) I created a node group that can add procedural snow to any imported terrain. The node group can be applied with only a few adjustments required to each new environment. This can be controlled on X,Y and Z axis, this is particularly important for the Z axis in order to keep the snow off of the sea.
See below the node group required to generate a snow layer:
I made use of an HDRI for improved lighting and set strength to 1.5, this is a sure way to bring out some lovely shadows:
For the snow layer BSDF node I turned the Roughness down a touch from default, and to ensure the snow is not too bleached out I set the Value on HSV to 0.7 which seems to give more realistic results:
Another example using real world data from Plymouth port:
Open below juxtapose at full resolution