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, 255/30 285/30
Performance Mods: Dinan stage 1 suspension, exhaust, intake; TTPs, BPMSport stage II tune; V1
Cosmetic Mods: OEM CF splitters, mirrors, center console; Arkym CF diffuser; OEM Edition grilles; IND painted reflectors/side gills; LUX; LED interior; tint