Neighbor Dave is right about the south and winter. As someone who has hiked the entire AT in the winter (Dec, Jan, Feb) the southern part of the AT is not all that hard winter wise. I've winter hike the southern portion three - four times (PA - GA). There are a few places such as the Smokies that might get hit with a good storm but on average most winter time
If this guy really wants to do a winter hike, he needs to do it over several years. What he is trying to do, I don't even know if he could be consider the young.
Wolf