While running one of the services on Dresden route, I noticed strange new fog effect I have never seen before. It was not foggy weather in general, as you can see in the first picture, however, as I was stopping in the first station on the route, clouds of dense thick fog started moving around. At first I though my train is on fire, it seemed exactly like that! Once moving again, the fog magically disappeared again making it look even more weird. While this effect would be cool to have in foggy weather, where it would blend easily into the general foggy weather in the distance, here I think it was improperly applied, as the visibility was obviously clear. It actually looks much worse in motion, than just here in the screenshot.
I think that happens in any snow conditions unless you have the wind set to zero. When I tried setting weather with snow on this route, as soon as I added the tiniest bit of wind on the slider that effect started in the diorama, so I left the wind at zero because I’ve never liked that effect even in the old blizzard setting.
Indeed, by why does it appear only at speeds of 5Km/h and less, and with perfectly clear visibility? When you accelerate it completely disappears.