I haven't noticed that at all but I do know that IRL you can have (and actually see) the lines in the fronts where weather systems meet and be in clear weather and see where the pouring rain is (check out some storm chaser videos). This also happens at sea (squalls) and you get lake effect weather near the Great Lakes and both land and sea breezes depending on the time of day (from both oceans and lakes).

When I lived in Utah you could see where the cloud line came down the mountains. Completely clear below the cloud line and thick fog (with a definite break) inside the cloud line.

I've noticed in game that right after sun up you can have fog and it usually clears up after the sun rises a bit more. I kind of like it. It keeps things interesting. If I've all ready eaten for the day and the weather is too extreme where I was planning on going I'll just portal somewhere else and do a different task on my to do list or I'll just garden and tend livestock.