Not too many people realize that it's best to get your brand new winter / snow tires broken in before the snow begins to fly.
New winter tires begin with deeper tread depths and more open tread designs than the tires used during the rest of the year. While the extra tread depth allows new snow tires to provide more traction in deep snow, it also contributes to more tread squirm and drivers may notice a reduction in handling responsiveness.
Before tires are cured, a release lubricant is often applied to prevent the tires from sticking in the mold. Some of the lubricant stays on the surface of the tires and traction is reduced until it's worn away. Tires are comprised of multiple layers of rubber, steel and fabric that require a break-in period to assure they achieve their maximum performance and your maximum satisfaction. A few hundred miles of easy acceleration, cornering and braking at no more than legal speeds will allow all of those components time to get used to working together, while the mold release lubricant wears off to help minimize the tread squirm.
Also, many vehicle manufacturer's owner's manuals recommend operating winter tires several psi higher than their recommended pressures for three-season tires. To gain a better understanding on why a psi of 3 to 5 higher is recommended for your winter tires, read "Higher Tire Pressures for Winter Driving."