late January is probably the most consistent weather wise. Early February is sweet too but after that it can be variable.
Sometimes we have amazing powder as late as April but If I were you I'd go late January. Less crowds too after the new year rush.
I think you'll love it.
You might see me at Nozawa onsen, If so I'll show you some sweet tree runs. I posted a vid of me in the other link you read. I wear the same Jacket and its pretty noticeable. Only trouble is catching me up
Let me know your dates when you have them.
I just go when the powder falls so hopefully I'll see you there.
Take some time to learn a few words of Japanese and you'll reap the benefits. Also learn the bathing practices for hot springs.
Don't step into any buildings with shoes on unless there is no place to leave shoes near the entrance or you see Japanese people doing so. If its a shoes off building (many old style restaurants and inns as well as all hot baths) there will be a noticeable step near the entrance. Take your shoes off there and put them where everyone else is putting them.
I often see foreigners do this wrong and the locals get pissed but the foreigners can't understand why.
Also wash yourself with soap before you get in the bath tub. Some young Japanese dudes don't do this properly but its correct etiquette.
Have a blast.