If the snow is that deep, that far down the road, would it be better (read safer from falling rocks) to park at Lone Pine Campground and hike up to the Portal? Just asking - I have never been up to the Portal in the winter but I do plan to go this year.
It all depends on how comfortable you feel driving up a road with a lot of rock fall, possibility of slides and being snowed in.
There are some who drive this road without chains, which think is nuts but that's me.
Generally, most will let the conditions dictate the parking situation. You can park at the most ignored sign in North America...something I never have done, at turn of the first switchback, past most of the debris at Meysan Trail parking area or the Portal itself. I seem to get Meysan Trail parking area most trips.