I too experience winter weather like yours. While the traction control and the overall weight distribution of the E36 model help in wintry conditions, I have found that all-season tires simply aren't enough, the smart and safe move is to get dedicated winter tires for all four wheels. That's the best set-up you can get yourself, either that or check out getting chains. Sure, more trouble than just putting on tires, but you can install 'em when you need 'em, take 'em off when you don't. Also cheaper than winter tires.