Ditto on what Alex said. I have a friend who rode a slide out on TDH mountain. I've triggered some tiny slabs on Hood myself. Don't be messin' with avy danger on Hood.
Any route on Hood can be climbed in winter conditions, some are even safer at that time. Depends on cajones and experience. I've climbed the lower portion of Yocum, Sandy, SS, and Leutholds in winter conditions. I prefer Hood with snow as opposed to without.
Jefferson is rumored to be pretty cool in winter but a longer time committment.
Close to Portland, Mt. St. Helens is pretty fun in winter.
Rob