Wegmans generally has it during the fall and winter, and I believe I have seen it in Harris Teeters also.
I know you didn't ask, so you probably already have a plan on what to do with it, but my favorite way of eating it is peel - slice into bite-size chunks - boil in salt water until tender - fry until golden brown in butter - yum!
Thanks for the info. And I do appreciate the cooking suggestion. I actually have no plan in mind; I've heard good things and have been wanting to tinker. From flavor descriptions I thought it might be a good starch to serve alongside a lamb dish I'm preparing. But it sounds as though I'm a bit late.