The roads are slated to open on April 15th (weather permitting).
The Park has two seasons:
Summer - auto travel
Winter - snowmobile and snow coach travel
It's closed between seasons:
http://www.nps.gov/yell/planyourvisit/hours.htm
Additionally, the facilities are currently closed:
http://www.nps.gov/yell/planyourvisit/open_closedates.htm#CP_JUMP_127493
WE NEED TO TAKE OBAMA TO TASK ON THIS!
So is 90% of Yosemite. Yosemite Valley is open but the rest of the park is under dozens of feet of snow. Tioga Pass into the park likely won't open till July 4th this year.