January and February are critical months on the training calendar. My coach will usually recommend increased time on the bike that includes some very long weekend rides. Unfortunately with the weather in our area, these hours are usually inside, and quite often reduced by 15 to 20% or so. What we don't compromise on is the intensity of the training intervals within those hours. The intervals can always be completed inside if the weather doesn't sccomodate riding outside.
Intervals in January and February should be designed to start the development of the skills you'll need for your event(s). If you plan on racing primarily crits, you may want to work on tempo efforts with high intensity sprints every 5 to 10 minutes. If road races are your goal, you may want to work on holding tempo efforts that will also incorporate steady state efforts and/or some climbing efforts. Time trial specialists may want to start working on steady state efforts and power intervals. The basic idea is to start getting your mind and body ready for the type of efforts you'll be needing once the race season begins.
In addition to some specificity training you should work on any aspects of your racing that may have been lacking in the previous year. In otherwords, you may have a sprint that is outstanding but an inability to ride at steady state power wont allow you to be in the right spot to use that sprint. Spending more time on some longer efforts just below threshhold power may help. You can also use shorter but more intense power interval efforts to increase your Vo2 and LT which will translate into better steady state power. The point is that there are a number of ways to improve your performance through interval training and the winter months are a fine time to start this process.