Hmmm, well where i live, we don't get a lot of snow, so i don't know too much about riding in snow. I'd suggest getting some thick boots for your horse, and try to clear paths that you want to ride on, and stay out of areas where there is really deep snow.

Also when horses have been riding in the cold, you can use my special bonding trick. Rub the horse's ears! Horse's ears are most vulnerable to cold, and rubbing them restores circulation. Horse's also love it, and will love you for it! Sory to mention that, snow being cold, just reminded me of it