Is it possible to have dynamically building snow on the terrain?

From all the ways I tried to make this work it's not possible. The only way that this worked was using a projector as Fattie suggested. HOWEVER, this effects all vegetation, along with anything else placed using the terrain, making it render weird with unusable results, even after I rewrote every shader that the vegetation used. It's impossible to set the terrain to a different layer other that what the terrain is because anything you place on the terrain using the terrain tools sets them to that layer. This means you can never change the layer of the vegetation so it's not affected by the projected texture.

You can't use decals, as they don't bend or contour to the terrain. Not to mention you'd lock any computer up with how many decals that would be rendered.

It's also not possible to lay any texture over the entire terrain. Unity's terrain is just too..protected, there is no way to change or alter anything. There's few things that are undocumented, but it's still impossible using all the documentation both documented and undocumented.

I tried using multiple terrains; duplicating the terrain as a mesh using a pluggin so I could have place my snow shader on the duplicated terrain, still impossible. Unity can only handle so many tris' (65,000) so you can only have a duplicated terrain with 1/4 the tris count making the terrain all blocky and unable to properly match the terrain, meaning you can never have an exact mesh replica of your terrain.

Until Unity allows more control over the terrain, it will be impossible to have dynamic snow on Unity's terrain. Believe me I have tried and researched for weeks, it just isn't possible, for now at least.

I'm posting this as an answer as, it's not possible. Hopefully this will help others so they don't waste weeks trying to do the same.