For park stuff around DC, go to Ski Liberty. less than an hour from the DC beltway. That's where all the local jibbers like to go because they cater more to the younger crowd. For more vert, longer, more consistant pitch terrain, go to Whitetail. About 90 minutes from the DC beltway.
To get to Liberty, take I-270 North. It becomes Rt15. Stay on that and turn left off the highway in Emmitsburg (National Fire Training Academy, Seton Hall Shrine, and Mt Saint Mary's college). Then follow the signs. To get to Whitetail, Take I-270 north to I-70 west. About 45 minutes later, take the exit for Clear Spring, MD. Follow the signs.