Where in Minnesota?
Reason is, I grew up in the Twin Cities until I was 15, and there ARE winter training facilities available. I can remember being brought in (required) from playing hockey on lakes outdoors when it got to around -20F, so lets say I don't spend to much time training there in the winter. But...
The Metrodome is OPEN FOR RUNNING two days a week in the winter. Can be used for SE/Special Endurance/IT I think. I do stuff like 4X2X150 IT/SE1 diagonals on soccer fields in California, and I think you can do the same kind of thing in the Metrodome.
http://www.runmdra.org/index.php/programs/12-dome-running
Facilities at the University of Minnesota also used to be open some of the time (but I'm talking about a looong time ago and it might have changed).
You CAN sprint in the Mall Of America--just put flats or something on. You don't even have to do it in the mall. Unless its REALLY cold outside (that's Minnesota really cold, not CA/TX) you can do it in the parking garage underneath downtown. There is a Skyway running club (or there used to be), and I think there's one in the Mall. (For folks not from the Twin Cities, there is a Skyway one floor above street level that runs all over downtown Minneapolis. It is heated and long enough to run. They also have a smaller one of these in Dallas BTW.)