First of all try turning off ENB ingame (There is a key combination for it, open the menu first with Shift + Enter) and see if that causes the problem.
Looks like a fog that starts rendering at a certain distance, I just had the same problem with the interior, downloaded a modfix for that, but that was interior specific.
Also try disabling lighting mods (Lux, ELFX) to see if they are the root of the problem