Snow tires

If the tires are all the same size you could install just 2 snow tires and still use 4WD. I would not but you could.

I have run four Blizzak type tires on Western New York (lake effect) roads, on every vehicle I have owned (4x2 and 4x4) since 1973. Due to there much higher traction, if you put high tech snows only on the front, you will watch your rear end pass you every time you touch the brakes. If you run them only on the rear, they will just push the front tires off the road. You already paid several thousand dollars extra for 4 wheel drive. Isn't your life worth $400 dollars extra.