I feel like your tire trail mask should be inverted. Doesn't make any sense that the tire trails would be leaving snowtrails and the surrounding pavement melted. Also you should cut down your trails or have them converge into one area. they really shouldn't be heading into the column and snowbank on the right. Also Bertrand did a good breakdown of a snow scene he did. It may give you some insights.
http://www.ronenbekerman.com/3d-snow-creation-tips-by-bertrand-benoit/I would also shoot for some more variation in the coniferous backdrop. Maybe some trees that have lost a bunch of their foliage mixed in among the rest.
Other than that, the architecture itself looks great and well executed.
*Edit Derp, Just watched your showreel looks like you ended up fixing the issues I outlined. Great reel by the way!
