I write this having absolutely no knowledge of how you plan landscapes, nor what you've already agreed on.
I came across this and just wanted to add a different perspective.
Scampy is correct in saying that "snowline" is a bad term to start from. A treeline looks like a line only from a distance. There is a gradient from closed forest canopy to treeless alpine tundra.
The primary causes of this are temperature and water availability (tundra, as opposed to alpine tundra, would have the permafrost problem preventing tree growth).
The higher the altitude, the thinner (the more spread out the gases are) and colder the air becomes (the gaseous molecules bump into each other less and the lower density means they absorb less solar radiation).
This resulting cold also ensures there is no available water for plant growth (being trapped as snow & ice) until the angle at which the sun shines allows melting.
Why am I going on about this??
Well, because the further from the equator you go (ie. less direct sunshine overhead), the lower the treeline.....
From a landscape design perspective, thinking about altitude and latitude can only make the end product feel more natural [for the game world], by ending up with more variation between different areas & regions that would otherwise be identical (especially the case with the mountainous/taiga mono-culture of Skyrim proper [I differentiate between the Reach & Skyrim] [although, mono-culture is also a bad term considering the diversity that exists between eastern & western Siberian taiga]).
To further diversify landscaping, there is usually a lower treeline on northern slopes (in the northern hemisphere) due to a shorter growing season (shade means ice takes longer to melt, less time for plants to use water).
High wind is another factor that keeps water availability down at high altitude, as well as eroding soil, both of which makes it difficult for plants to colonise. It can also have the effect of keeping ridgelines snow-free, while a snowfield would be found on the leeward side of a ridge.
Again, I hope you take this as a constructively different perspective, that may help inform future plans.
Last edited by dobren
on Mon Jan 15, 2018 11:29 pm, edited 1 time in total.