I am in southern Middle Tennessee; we're in a lot worse shape this year than 2011 --- a lot worse shape.
If you haven't read the "Feeding TMR's" thread, here's the link. The Horse | Forage-Based Total Mixed Rations: Economical and Effective
It's something that needs read in its entirety. This is not the same as a ration balancer and, to-date, only appears to be available thru two feed companies that are named at the end of the article.
You're in a tougher position because you board. And trust me, you're going to have to keep your horses' feed stuffs at home if you don't want them to do a disappearing act. Padlock or no padlock, if someone gets desparate enough, there isn't a lock that can't be broken
Rather than straight alfalfa, you might consider timothy/alfalfa cubes by Standlee. Tractor Supply carries them.
Whatever kind of hay forage-n-a-bag you buy, I might plan on turning a spare bedroom into a storage area and keep enough to get you thru winter. If it's forage-only (not those Lucerne hay bales with molasses in them), it should keep all winter without issue.