Living in the Seattle area, we don't have to deal with snow much. When I was a kid in Alaska...if you let some snow stop you from doing anything...hang it up!
There was one spot in downtown Anchorage that seen a lot of use with festivals and the like throughout the year. Now Anchorage can go clear into December without seeing much snow. (I still detected some even though the ground was either hard or spotty and found stuff.) Surface jewelry was about the only thing I looked for but clad was there a bit.
There is one type of hunting that can only be done in winter and it can be some of the best hunting possible! Snow removal piles from parking lots are something else! It is best to wait till some melt is going on as this kind of renders the piles down but "heavy" still settles regardless and great times can be had. Best advice here is to develop permission to get in to these spots and keep your mouth shut! Again...didn't do much of this myself but knew people who did.
When it comes to finding platinum (or other extremely low conductors) most of it is rings. I personally have never found anything platinum, but others I've met have and those are special finds indeed. You can go on and on about discriminating this from that and that from this but in the end, almost all rings have only one thing in common...tight VDI's no matter where they show up on the "scale". There is something very important for the jewelry hunter on having a VDI or metered response machine, because of this, and that alone is about the best reason to go with at least a midrange machine for even occasional jewelry type hunting. One huge advantage (with jewelry) is detectorists, in general, are way to "coin" oriented. Jewelry finds can be pretty consistent............ with the right mindset and retrieval speed skills.
I would probably be a little slow to get out and hunt in the snow these days but...funny what a killer spot can make you do! Good luck in the snow!