One way to create dynamic snowdrifts in UE4 from Andre Allan.
Andre Allan has uploaded a video tutorial on working out landscape snow deformation using render target. It is a really nice way to create dynamic snowdrifts.
I saw some that where interested in this. I know its mostly more of the same, but it is again a bit different way of doing it. I can see why some want to have the options to do it directly on the terrain. It should be precise enough for most things, but I find its a bit of a step backwards in some ways. But it works as it is.
There are other ways to work with deforming snow, of course, but this one works just fine. Make sure to check out other guides by Andre here.