Absolutely one of the best things you can do, if you live in a snowy or colder climate, is invest in a set of dedicated winter/snow tires & wheels. And as others have said, all four is the only way to go. There's fantastic information on TireRack's site about the advantages of running all four tires vs. just the front or rear (depending on which wheels are driving your vehicle) and once you read it, things make sense.
As a side note I'm glad I don't live in the "Big City" in WI and have to worry about Elizabeth being on the road at the same time as I am. Anyone who says that high performance summer only tires stop, start and corner as good in the snow/cold as a set of dedicated winter tires do is out of touch with reality or in some serious denial.
'14 Mustang V6 Prem. Perf. Pkg