Once you get the rust knocked off the the deice procedures and stuff we don't use for the other three seasons, winter ops aren't usually too complicated (unless it snows in SEA or PDX), so if you're already familiar with part 121 winter ops, the only real change would be QX or Q400 specific procedures.
Aside from just flying, most of the upgrade to captain is about your ability to manage, be it the airplane, the crew, or an abnormal or emergency situation, so it's really down to how confident you feel in your ability to do that.
If you're confident in your ability to fly the airplane and manage everything (especially the FMS, since new FO's will struggle with it), you shouldn't have a problem with the upgrade, but if you're still adapting to our SOP's and aren't comfortable with the Q400 and its various quirks, waiting a little while would be a better idea than attempting an upgrade you're not ready for.