We didn't get that much snow on the NW side of town - how much were you driving through? Because the tires on our cars are pretty wide, they can "plow" some. If one side of the car hits more snow, it can cause the car to "dart" some. That's about the only thing I can think of.
2010 E90 335i Black Sapphire
COBB/PTF proTUNE/Alpina/BMS Drop-in/PSS/Blizzak
Best Stock 1/4 time = 14.1 @ 99.4 at Bandimere Speedway (DA = 7,400ft ASL; 13.5 @ 103 corrected)