Sounds nice.
I have to say Sendai.
At that time the lights are beautiful and there are the Pageant of Starlight (12.12 - 25.12). All of the trees of the whole Jozenjidori are lighted.
Of course there are the march of 300 Santas (23.12) at that time. Just buy a Santa outfit and join them

Don't forget the izakayas (bars) of the Kokubunjo and shops of Ichibanjo

From Sendai you can go to nearby famous ski resorts of Mt. Zao (Yamagata prefecture) and Mt. Bandai (Fukushima prefecture) or enjoy smaller ski resorts closer.
Some places to go are:
1. Yamadera (Yamagata prefecture), beautiful temple made in top of a mountain.
2. Akiu onsen (Miyagi prefecture), famous lord Date Masamunes favorite hot spring.
3. Matsushima (Miyagi prefecture), many islands covered with pines. It is wery beautiful as Matsou Basho wrote to his famous Haiku: Matsushima ya, aa Matsushima ya, Matsushima ya. (The meaning is that Matsushima is too beautiful to describe.)
4. Aizu-Wakamatsu (Fukushima prefecture) Tsuruga castle is my special favourite. Is as original as Himeji castle but in more beautiful surroundings.
5. Naruko onsen (Iwate prefecture), really nice hot springs that are famous for whitening the skin.
6. Hiraizumi (Iwate prefecture), the most East spot of the Silk Road. Hiraizumi once rivaled with the glory of Kyoto.
7. There are many good places to go in Sendai too: Dates mausoleum, Rinnouji zen garden, the sight of Aoba castle, etc...
8. Shiroishi castle (Miyagi prefecture), nice little castle witch was a residence of a samurai.
9. Ishinomaki (Miyagi prefecture), the place from where lord Date Masamune sent a convoy to travel and meet the Pope to Roma (3month later the Christianity was banned in Japan). Also famous for being a manga city.
And lot's more

A slogan from Sendais ad:
"Joyful trip
SENDAI
Smile is to bring a happines"
So you should definitely go to Sendai
