Swain, NY is a tiny ski mountain in soutwest NY with some short, smooth, flowy DH runs and one hell of a moto track. The moto track is actually on the ski runs, and is pretty techy with lots of step-ups, step-downs, and rhythm sections running up and down hills. 3 hours from Watsontown.
Ellicottville is another hour west from Swain, so you're talking about a 4 hour drive from Watsontown. It's one of the IMBA epics and has plenty of riding to keep you occupied for a few days. Not too hard to put together a 50-mile ride in E-ville. No shuttle or lift-access gravity runs, just awesome XC trails with some descents running 3 miles in one shot.
For supergnar, you want to check out Plattekill in the Catskill Mountains. 4 hours from Watsontown. Steep, rocky, gnarly old-school DH with ZERO super-groomed buffed-out stuff. It's the type of place you will never truly master. Wear your armor.
Check out the UCI World Cup at Windham, NY June 30-July 2nd. Best riders from all over the world racing, and there are citizens' DH and XC races as well. A bit under 5 hours from Watsontown, and totally awesome experience. Volunteering (say...course marshall/front-row spectator) gets you good parking/camping spot and free food and drink.
Diablo Freeride Park is in northern NJ has techy DH runs as well as some awesome groomed freeride runs with ladders, skinnies, wall rides, doubles, drops, tables, you name it. 3 hours from Watsontown.
Shindagin Hollow near Ithaca, NY has some awesome XC trails for an all-day ride and even has a gravity run or two. There are trail maps, but it's still best to go with a local the first couple times. Less than 3 hours from Watsontown.
Oneonta has great XC/AM trails; we've gotten to the point where we can put together almost a 25 mile ride without too much repeating or road riding. Lots of new trail built by bikers for bikers. That means plenty of optional lines, potential for air time, skinnies, rock sections, berms....3.5 hours from Watsontown.
That's all I've got off the top of my head, without heading farther north.