I would think as long as your VS flight arrives the night before you'd be pretty good to go. Even with massive delays total closure for extended periods 12+ hours are rare. I would try to get EWR as early as possible on Saturday becaus eyou never know which flights might get cancelled because of fear of stranding aircraft at EWR.

Watch the weather. The confidence level in the forecase increases as the storm approaches. A few hours either way on the start/finish of the storm could male a big difference for you.

As others have said if you get on a Sat to London go for it (although if you are on VS would CO taje tou standby??). Also keeo checking to see whn, of if, CO wauves change rules because of the weather. That's when your flexibilty might increase both to your ticket and the availability of seats.