If can be done from Turf (Phoenix, Az) on a good day - but you would
have to be on an IFR clearance to do it legally. Turf is at 1600', and
I've seen cloudbases above 22,000' (FL220) on a good day up by the
Grand Canyon (an "easy" 2-3 hour flight from Turf).

There has been some talk of arranging for a "Thermal Window" that would
make this easier to do.

Kirk