You would probably lay a very solid foundation for outdoor track if you did the same thing you did in the summer.
If you wanted to tweak things a bit, I would recommend introducing hills (@5-7% grade; 1:00-1:30) once/week. Initially, run them at 1500-3000 effort and don't worry about the recovery times. Focus on being powerful and efficient. From experience with many high school runners, I would expect your times to be roughly equivalent to your 5k track pace if you are running ~400m on a 5% grade or ~250m on a 7% grade. Obviously, if you're dealing with snow, ice, cold temps, etc. that won't be true.
As you get towards the end of January, start restricting the recovery intervals a bit but don't try to make it a major anaerobic workout. As you get stronger and adapted to doing hills, you should just naturally need less recovery. Keep the focus on power, form, and efficiency.
This is also a good time to introduce any additional strength/flexibility work you have been considering: new core routines, plyometrics, weights, yoga, etc.
If you are in an area with winter weather than can significantly hamper your ability to get in hard workouts, I would suggest planning out an entire week at a time and adjusting the schedule to the weather. You can always slow down an aerobic/recovery run without losing any signficant benefits, but trying to hammer out a tempo run in 6 inches of snow is another matter.
Good luck!