Winter Roads and dioramas

There is a couple of products you can use as snow. (It seems everytime I try to help someone with their dio, I turn into the Woodlandic Scences poster boy). Anyway, Woodlandic Scenes has snow stuff you put in a mixer shaker thingie (available at your LHS) and you sprinkle it on. Just don't put it where you don't want it to go. simple enough; lets see here. There are a couple of ways to put slush/ thick mud on wheels. One is to go to this web sight so I don't spend all night trying to tell you something I've never done before.
http://www.armorama.com/modules.php?op=modload&name=Sections&file=index&req=viewarticle&artid=100
All in good fun. Now that should actually cover all your questions. If I were you, I would also post this in the armor thread and say that "I've posted this in the dio thread and didn't get enough info". Leave this one here of course. At least there you'll get a lot more answers to your questions. Mkay? Have a great day!

Things to remember:
Slush and mud are two very differnt things and behave differntly. Slush tends to fall off warm surfaces very quiclky, mud is more likely to adhere.
Smow and heat don't mix. There should be no snow on any exhaust part, noe cloe to engine vents and radiator parts. Snow slides of angled surfaces quickly when there's any warmth. Snow does not stay long on round surfaces, like gun tubes except in the midst of a snow storm.
Snow doesn't stay white long in the face of any kind of traffic. Compressed, sliglty melted snow is silver grey, muddied snow, where splashes have occured in dark brown to blackish.
Metal transmits and holds heat very well so snow on a vehicle is a transient situation. Rolling wheels create heat through friction. There should be no snow or tires or tracks.
Unless you've just had a windblown snow, there should be no snow on verticle surfaces and then, one or two angles of the tank should have no snow at all.
Except for the most crusted examples(resulting fromn periods of freezing rain/sleet, snow will nut support a human who is not wearing skis or snowshoes. Certainly a tank will sink to the depth of the accumulated snow less the compaction factor. 12:1 is a good compression ratio.
Snow s@(#s!
Mud, IMHO, is almost always over done in dioramas. Builders look at previous builders' dioramas and want to make theirs "More realistic" by adding more mud, getting further from the facts.
Anyway, check period photos. The amount of mud that can exist will depend on how warm the day was, how much snow was available to be melted and how cold for how long it had been before the time in question.
The more melted/warmer the more mud, the deeper you have to place your tank in the mud and even your figures.