I've lived in Indiana for most of my life, and it has some of the strangest weather patterns you'll ever see. Layering will become essential, as smahanru mentioned, because of the buildings but also because the temperature will change by 20-30 degrees during the day, depending on the season. Its freezing in the morning and night, and more bearable during the day.
From the end of december to mid march, I don't think a leather jacket will be warm enough, especially to someone who is used to warm weather. You'll probably want a wool peacoat or a parka-type jacket for the mornings and nights. 30 degrees is alot colder than you realize before you go and walk around in it for 20 minutes. It's not like the northeast where you always need a hat, scarve, gloves, and coat to even go out, but you might consider buying a cute pair of gloves, as my hands always freeze to death in the winter, especially walking to classes.
Like mentioned above, it depends how well you deal with cold weather, but i'd say get something more than a leather jacket.