Where to get a long run in during on Sunday during the NYC Half?

Hi! I'm out of town this weekend and returning Sunday morning to the UES. This is my first time in 3 years NOT running the NYC Half :( (bummer, didn't get in this year). However, I am training for an April Marathon and really need to get a long run in on Sunday. I usually run central park or along the west side. Any ideas of where to run on Sunday without running into half marathon barriers? I need to get in 18 miles.