The elevation is a killer and the 70 is a small battery. I think you're going to have real trouble on the way up. Should be no problem at all in the other direction though. You might want to stop somewhere on the east side of PHX metro to charge to 100% before going. Then drive slow, don't use the HVAC and keep the suspension set to LOW. If it's really cold or if there's any precip, you probably aren't going to make it.
It might be wiser to try topping off in Payson. I'm sure there's something available. Take a look at Plugshare.