Why are you consider A/S instead of dedicated winters? Sounds like you'll be still using summer tires for the warmer months, not using A/S year-round.
There are a few tire options for 19" winter setups. On ZCPs, I'd use 255/35 and 275/35 Blizzak LM60s. Or get a second set of wheels to allow a narrower tire for improved snow performance. Depends on your how you'll be using your M in the winter.
Do a search. There are plenty of threads on winter setups. Good luck!
2011.5 E90 Dinan M3, SS II, M-DCT, EDC, M Drive. 20" MORR VS8.2 wheels
Performance Mods: Dinan St.1 suspension, exhaust, intake; TTPs; BPM St.II, DCT, servo tunes
Cosmetic Mods: OEM CF splitters, mirrors, center console, spoiler; Arkym CF diffuser; LUX; tint