Like the sand desert snow covered terrain provides extra challenges for defenders as the ability to travel quickly by ski/oversnow vehicles, just about anywhere, vastly increases the area you need to watch.
In Norway we regularly skied full battalions through mountain ranges, in excess of 40 kms in under 24 hours, to appear unchallenged in the rear echelons of OPFOR formations. Long periods of winter darkness, about 16 hours, helped alot too of course.