I basically agree with all the suggestions that you not drive in snow with summer tires but I also think it is possible, just not advisable. Here's a link to an actual test:
There is a big difference. But the driver makes a difference too. You cannot drive like you do on dry pavement regardless of what tire you have. And if you are really careful, you can make the car go with summer tires. But why risk your nice car? You need at least all seasons.
128i Convertible, MT, Alpine White, Black Top, Taupe Leatherette, Walnut, Sport
Ordered 5/22/09, Completed 6/4/09, At Port 6/9/09, On the Georgia Highway 6/13/09, Ship Arrived Charleston 6/24/09 at 10pm, PCD 7/21/09