After the 4th there are currently three resorts open in North America with terrain parks.
Of course there are plenty of unofficial hike to terrain (tuckermans).
Of the three two are lift served.
First on the list is the only outdoor lift serviced year round resort in America.
Timberline is on the palmer snowfield on Mount Hood.
They have a full halfpipe, a huge terrain park and temperatures of 58 currently.
It is serviced by a high speed quad (and a ropetow for the camp).
The features get raked consistently.
They also say the hike park will most likely remain open till opening day.
Third on the list is Big Snow American Dream.
The only indoor resort in North America.
They have cool temperature of 28 degrees.
In addition to a good park (14 features).
Its lift served by a quad, platter lift and two carpets (the platter almost never runs).