by AlmostThere » Wed Feb 29, 2012 4:31 pm
If it is your first time in Yosemite, have no desire to be in winter conditions, and do not want to go to Hetch Hetchy (which is not going to be a 3-4 day backpack until spring, unless you are going to follow the trail up into snow) then I strongly suggest just being a tourist - day hike. There are lots of one day hikes you can do as early as April.
This year there is hardly any snow at all relatively speaking - usually the high country gets 6-12 feet of it - but this last week has seen a couple of feet of snow, and there may be other small storms depositing more soon. If more than a foot of snow accumulates the trail will be obscured above snowline and shoes will get wet and soak through if they are not waterproof. Night temperatures will be quite cold until spring, ranging from 10-25F, at around 6-7000 feet elevation (most of the park is at this elevation or higher; snowline is usually 5-6000 feet). April is considered winter in Yosemite and you should have snow chains or cables in the car if you bring one. There may be ice in shady spots here and there, and the Mist Trail to Vernal Falls will likely still be closed due to ice in the steps, even if there is no snow at that elevation; there is a detour trail that will get you beyond it.
I recommend finding lodging and planning to ride shuttles around and doing dayhikes - Mariposa Grove, Yosemite Falls, Nevada Falls, etc. Tioga Road will not be open. Glacier Pt Road is rarely open in April.