In real life there isn't a limit to how deep snow can be but in vanilla Minecraft there is. If you want to make Minecraft more realistic by having it so that it can snow much deeper then you should try the Snows Deeper mod for Minecraft.
Download for 1.7.2
Download for 1.6.x
Download for 1.5.2
If you don't know how to install Minecraft mods read our tutorial.
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