Sandy, for your setup you could easily provide bales for shelter, assuming you have some older ones you'd be prepared to sacrifice because of droppings. Make them a little 'fort', if possible up off the ground a distance, and provide some 4x4's or 2x4's flat side up as roosts. Be sure everything is knock-proof and wind proof because even a barn cat can get something unstable to fall. They'll feel safer at some elevation in a barn so take that into consideration.
My heart goes out to you, we're just coming through this and 14 snow storms. We got through without losses, but it was a battle.
Another option is to baffle their roost space with sheets of *heavy* clear vinyl, such as 12 ml, or tarps. If you have any spare OSB or plywood it might be possible to build them an elevated platform or 'house' with baffled sides. It *will* make all the difference.
The other thing of course is keeping the water liquid. It's a must, even if someone has to go out there several times daily with warm water. They are going to eat,. eat, eat- you will be very surprised, they should not be without food and water at any time through this.
Some other thoughts here:
https://www.backyardchickens.com/web/viewblog.php?id=7693-seasonal-concerns
Stay safe!