I just dug up the last of this year's carrots. Why don't I ever plant enough to make it through the winter??? The last harvest is always full of the tiny rejects... the little carrots I didn't bother pulling in earlier harvests. They still taste good -- tiny but sweet. I like nantes, so that is what I plant. They are super sweet and crisp, and I have had good luck growing them in very loose soil, both at home and at alleycat acres. Don't bother if you have any sort of hard pan. Carrots like their soil loose, and won't stand for it any other way.
Carrots are nice for us urban gardeners because they store best in the ground. Plant them in late summer and leave them outside all winter long, harvesting only what you need. To protect against hard frost, just give them a good mulch before the snow comes (don't bother if you live in a mild climate).