It’s not snow that yours are afraid of, it’s change. That’s normal with chickens, though some handle change better than others. When mine wake up to snow for the first time they don’t like it. I open the pop door but it may take them two or three days before just one builds up the courage to step on that weird white stuff. Eventually some will go outside and walk around in it, but my snow usually doesn’t last a long time, normally just a few days. Some may never go out in it.
But this snow fell during the day and they were already out. The change was gradual enough they just accepted it. Just give yours the opportunity and let them decide what to do. They will be OK. Their behavior sounds very normal.
It’s fairly common for some pullets to skip the molt their first fall/winter and continue laying. It’s also fairly common for some pullets to molt their first fall/winter and stop laying. Looking at those photos its possible you may have both going on. But there is another possibility too. A few of those look like they may have already molted and could be back to egg laying. Not all chickens in a flock molt at exactly the same time. Some can start and finish a lot earlier than others.
What I think happened is that a few of those started molting a long time ago, are over it, and just started to lay again. The others waited until recently to molt so they look really bad and have stopped laying. Think about how many eggs you were getting and how many you are getting and see if that makes sense.
With those feathers laying around yours are molting. It seems with that loss of feathers that they might be cold in your weather. There have been some threads on here with people a lot further north than you with that going on. They don’t heat the coops or anything like that. Some make sure there is decent bedding on the floor so they can snuggle down in it if they wish, but others don’t worry about it. They may have originated in jungles but those jungles were not always hot. They really can handle cold really well, even when they are molting.
There is a certain breed of chickens, called Turkens but sometimes called Naked Necks. These have no feathers on their neck, just bare skin. The feathers they do have are about half as thick as regular chickens, yet they are considered cold hardy birds. Personally I’d make sure there was wood shavings, straw, some kind of bedding that they can snuggle on together if they need to but I would not over worry about them being cold. Give them some options and they can handle it.
I’ve butchered a lot of chickens, hens, roosters, pullets, and cockerels. Once you remove the feathers they can look pretty skinny, especially the hens and pullets. Compare the ones that are molting and the ones that are not molting. Does one of these groups look fatter than the other? Think about it.
The only thing I’d question in all of this is why did your pullets wait this late to molt? The main reason they molt is that the days are getting shorter. Actual length of day is not all that important, it’s that they are getting shorter. Days are now getting longer but yours probably started a while back.
Stress can help trigger a molt. Did something happen a few weeks back to stress them? It could be something like running out of water for an extended period of time (probably more than a full day), a change to housing, adding or removing a chicken to upset the pecking order, maybe a predator attack or threat. They don’t like change and change can cause stress. It could easily be something you are not at all aware of.
What I think happened is that most of yours were going to lay all through the winter until something stressed them. That in conjunction with the days getting shorter was enough to kick them into full molt mode.
I’m across the internet so I can only guess at what might be going on. I could easily be wrong. Even looking at them it’s not always easy to tell. But I don’t see that you have a lot to be worried about. Since it is your first winter with them I know that doesn’t help a whole lot but I think you’ll be more relaxed about them next winter.