The snow is a bit odd. Ideally, snow specularity should be almost unnoticeable, as light hits the snow and spreads throughout, rather than it hitting it as if it was a solid mass. (Which gives you smooth highlighting.)
What people usually do, and what I think works pretty well, is they drop specularity altogether, and simply make the diffuse of the snow ludicrously bright. Especially with an rts, where you're essentially never going to have an area where the geometry is complex enough to constitute more complex specularity. Then, turn down the ambient lighting so that the shadows are very contrasting. (Skyrim did this a lot.) The problem is that snow has a pretty intense sub surface that captures pretty much all of the light that makes it appear white, so its hard to light it correctly with solid polygons. Currently, it sort of looks like glazed frosting. But, if you fake it, it should look pretty sweet. Don't be afraid to make it fairly monotone, I guess. Dark contrasted shadows should take advantage of that.
Granted, I have no fucking idea how spring's shaders work, and I also don't code for shit, so this applies on my end.
http://www.angelfoodcomic.com/wp-conten ... -doing.jpg