I don't know what section of Pa your from so I'll give you some general thoughts; If your in coal coountry you could try coal shale to bed then blend lightly, if you have conifers around or can get to some cedar/junipers you can get the black leaflets from under the trees to bed and then blend, you also can mist with glycerol or polypropolyene between sifitings. Maybe a combination would work in extreme freeze thawing.
I routinely use juniper needles and/or waxed dirt. In all cases you will have to blend over and as Jim-ne pointed out when the covering gets wet and freezes you will experience some problems. I use night latch trigger arrangements to minimize the movement needed to trip the trap and I four coil most of my traps to get them through lightly froozen soil. Remember to dig your beds a bit deeper/larger and add a good layer of what ever you try in the buttom/sides to retard the wicking of moisture from the surrounding ground. I have little trouble when I use waxed dirt. However, different soils and mooisture will change things. Wish I had a fool proof fix for you.
