http://diggy.i2p/articles/smolensk.xhtml
You might want to say that the Ilyushin could have also created the fake fog, but that would be dangerous to the Ilyushin as well, so they had to create it from the ground. Keep in mind that this is just my amateur analysis, meaning I could have missed some other possibilities. And, it could also be a combination of all the three options. What's for sure is that this stuff wasn't fucking snow.