When it snows the traction can get better in some places but you will definitely have to up your game on riding with the bike sliding around underneath you. This seems contradictory but what you soon realize is that even though you might be sliding around in the corners, it's predictable and consistent. That consistency is key to being comfortable on a new surface. The more you begin to trust what will happen in given situations the more comfortable you can be expanding your comfort range.
How to ride the snow? Stay loose on the bike keeping the elbows, wrists, hips, knees, ankles, and shoulders active. You have to be ready to let the bike choose it's own path sometimes and counter-balance becomes key to survival. Angling the bike underneath you is critical to keeping yourself out of the snow. For a good counter-balance drill go into a field and practice riding slowly around in circles changing directions to transfer weight and the angle of the bike. When I say slow I mean agonizingly slow. This might be best to do on flat pedals or without your mtb shoes so you can put a foot down easily. Try starting to slow down to a stop then pedal away without putting a foot down. Do all of this while staying out of the saddle.
A counter-balance drill that benefits snow riding!
1. Choose a gear in the middle front ring middle rear cog region.
2. Go flat pedals or non clipless shoes if you're afraid of falling over.
3. Choose a place with a small incline.
4. Pedal as slow as you can. I call it the slow game.
4.5. Be sure to do most of this out of the saddle.
5. Counter-balance your weight by angling the bike but keeping your hips above your feet.
6. Practice slowing to a stop, then starting again without putting a foot down. Try pausing at that stop longer and longer while staying balanced.
7. Change directions frequently.
8. Do this with a friend, playing slow follow the leader. Try to trick them into putting a foot down.
This is the philosophy behind doing skills and drills in parks. If we were to try and practice on the trail there are constant variables that effect your attempt to practice that one skill you are trying to dial. In a field we can set up an obstacle and eliminate almost all of the variables so that we can get down to the business of learning the key movements needed to perform certain skills. Consistency is key! The snow is a big variable, but you soon realize it's an equalizer that blankets your trail. Don't be afraid of the snow, ride it and learn new things you'd never have the opportunity to practice over and over again without it.
Why ride in the snow? There are several good reasons to go out when the conditions get weird! For one it's good to change up the routine and introduce our bodies to new problems and experiences. Without having to drive some extra distance the snow changes your regular riding trails into a completely new place. The corners have a different dynamic, snow has filled in some choppier sections and smoothed out those spots that normally suck your wheel into momentum blackholes. I often find myself taking new lines in the snow I would never use on regular dry days. Contrary to surface logic, traction can get better, depending on the snow conditions.
Two factors effect the possibility of riding in the snow on the ground. Depth and consistency. A light fluffy snow that's freshly fallen can be ridden in at depths up to 5 or 6 inches, sometimes more depending on your leg strength and tolerance. That fresh snow will part nicely for your tires as you plow through. As the flakes get bigger and wetter and the depth grows a fun ride can quickly turn into a slog.
On the far end of that consistency range is the deeper snow that has been through a warm day then frozen to form a crust on top that can actually support the weight of you and the bike. This is a rare but magical event you'll never forget. When the snow is like this you'll soon find yourself leaving the trail riding through the woods in places never imagined.
When the snow gets to deep, be happy because it's a good chance to play on the cross country skis. If you're a mountain biker and you haven't given the XC skis a chance you owe it to yourself to try. Imagine having the ability to go places your bike never went because there were no trails? A whole world of exploration awaits!