Replying to 5 feet high enough for a drop in?

Alright, so my backyard set up just doesn't cut it, so Im making some really nice boxes and I need a good drop in. Im planning on making it 5 feet high around 3x3 at the top, and the ramp going down would be about a 45 deg angle and 2 feet wide. I plan on making it so the drop in is portable so I can use it for urban. Is it high enough to get on a 1.5 foot tall box using astroturf and sometimes snow? thanks in advance.