Prince William CG- Dumfries, VA
Good to know that the Prince William Forest National Park RV campground is open in winter. We camped there in the past (during October). The other campground (Oak Ridge Campground for RVs in Prince William Forest) was closed this winter from December 1, 2014 till March 1, 2015.
Americamps- Ashland, VA
The Americamps is the KOA I mentioned in my earlier post (its called: Americamps KOA).
A good selection of camprounds along I95 in NC, SC and GA are open (if you need an emergency stop: unplanned ice storm or snow). We prefer to dead-head it right through those States to FL, because they are often nailed by ice storms/snow from January through February (if we have a clear go of it weather-wise, we count our blessings, and don't linger in this geographic region during dead of winter)...St Mary's Florida is a nice long drive, and good stop if we leave Virginia very early in the AM, and I don't mind long drives-- if weather isn't too taxing on the nerves and my back.