I come to necro this to say that THIS WORKS for me in 2024 still!
Shadow pop-in distance can easily be changed in the ini, but it doesn't affect the fog layer.
setfog 0,50000
is my preferred setting so far, it doesn't take long to type it out real quick when booting up the game and the weathers still have varying fog levels. It's less dense/thick than the default value I think, switching back and forth during foggy weather implied that default setting is a lot thicker than the 50k.
I can also confirm that 5k is peasoup. xD Don't reccomend. lol
(also note that it's written with a comma and not a point!)
I hope that this necro will help other people to stumble over this thread FIRST instead of having to read through half a dozen others that have no answer.