Google Search shows several Truck POPUP Campers in the mountain snow... This one article is kinda neat reading...
Colorado Camping in TC Popupwe have camped alot way into the winter months in our OFF-ROAD POPUP camper trailer... No problems at all keeping warm. Our Battery Bank is 255AHs Capacity and carry a 2KW Generator to recharge the batteries each day using the on-board trailer smart mode converter setup.
The battery bank and INVERTER setup allows us to use a couple of electric blankets that is nice as well... Our Propane Furnace is actually too hot for us and hate the loud BRRRR noise coming from the blower. It is actually our last resort heat source with thermostat turned down real low to only come on if temp gets below 35 degrees or so...
We only have one fresh water tank to deal with so can drain it and use the blow-out method for the small foot print water system. Can go right back to using fresh water tank again the next day by just adding water..
Don't think you will have any problems keeping warm with the Truck POPUP camper.
Roy Ken