Anthony!!!! As a Canadian I am shocked by your question. "What's under the snow?" Look around you. The reference material lasts until mid-April. Even Mississauga gets snow!
Okay now seriously. As was previously mentioned taller items always poke through. Now the next question is what is being moved through the area. If it's armour, obviously some of the snow and the turf underneath will get ground up and mixed together. If there is a construction site near your house take a walk by the next time it snows and note how the snow is trampled and changed by the workers and machinery. You can use this as a reference for tracked, wheeled or even foot soldiers.
I build all of my groundwork the same way. I lay out a blueprint in marker as to what is where and it creates a paint-by-number template. So using this method I first lay out the overall ground cover earth first, stones or small pebbles, roots or trees, then static grass, taller grasses, then heavier things - equipment, downed branches, rubble, etc. Then the figures and/or vehicle(s). Once everything has been added I remove the figures and vehicles and sift on the snow. I use marble dust from a local marble counter supplier. It's free and it doesn't attract bugs like flour or baking powder will. Once the first snowfall is over I spritz the entire area with a 50/50 water and white glue solution from a spray bottle. Then add the figures, vehicle(s) and apply snow again to blend the figures and vehicles in.
Hope this helps.
Cheers;
Gregory