IMO, I would leave them in. Why take a chance on the viscosity of the fluid breaking something. If it does snow, then you just got one more thing to deal with before turning the key and heading down the road.
I have been told the furnace is setup to run with slides in even. Don't know if that's really true or not, but would think it is. I would not put down the jacks in the rare case they might freeze to the ground.
If you got electric you should be fairly warm. Set the furnace low and let the electric heaters keep you warm. Close off doors and keep your personal area toasty.