Bunny runs open with 3' of snow.
Blue runs need 4' or more.
Anything black, usually 6' of snowfall, and it can pack down to whatever....3-4, and work.
Expert runs, not down the middle of the runs, need 8' + of pack to clear the rocks.
Powder covers lots, but your ski/board can easily sink 2' or slightly more in slow spots and turns.
If you plan to ride 11 or 6, hike up off 4 at Kirkwood, you have to wait another storm or two.