Last poster was correct.
Low intensity, long rides. If you have to do a video, I suggest the Chris Carmichael (CTS) Tme Trial Video. Lots of sitting in the saddle, cranking away.
Also, you should add some strength training into your winter workout.
If you are jonesing for some some interval work, and you belong to a gym, see if they have Spin classes. Do that class once a week and you'll get your fill for intervals.
The problem with doing intervals and speedwork over the winter is that you never build your base, and you'll burn yourself out by the early spring.
Your first couple of spring races should be training races really. You probably wont get your "legs" until late spring/ early summer. Any sooner than that I fear you'll be toasted by mid summer.