Shouldn't be much of a problem if it's not cold and you keep the speed below 50mph (4.5 miles per kWh on flat ground)
The rule of thumb is 1.5kWh burned for every 1000 feet gain for the mass of a LEAF, in addition to normal consumption on level ground. Las Vegas is 2500 feet-ish, and the top of the drive can be up to 8500 feet-ish, so 6 thousand feet is the difference multiplied by 1.5kWh per thousand feet consumed equals 9kWh... JUST TO MAKE THE CLIMB!!!
To drive the 38 miles at 50mph / 4.5 miles per kWh consumes an additional 8.5kWh with NO HEATER USE
(seat heaters are OK). The air conditioner is very efficient, and it will cool off as you climb, so I don't recommend turning it off.
Total consumption at the top of hill - 17.5kWh
Miles per kWh on dash at top of hill - 2.2 miles per kWh
I want to be clear that 50mph isn't an average speed, or top speed... it is the
speed. So, if you have to slow down and accelerate out of turns, the consumption is likely to be higher (lower "miles per kWh"). If that is the case, I recommend an even slower speed, maybe 45mph max.
The new 2015 LEAF holds about 22kWh when new with a warm battery. You have about 4kWh to return to Las Vegas, or about 9.5 miles per kWh !!!
Yes, it can be done, but this is NOT a casual unplanned drive. Plan the drive and drive the plan.
This is somewhat similar to the two times I've driven to Julian, California:
LEAF to Julian
I used 9 bars on the climb, and drove 41 miles from my house at 580 feet elevation to Julian (over 4000 feet elevation). The Guess-O-Meter was showing 18 miles remaining and 3 bars when i started my 41 mile return.
I did about 20 total miles of pure coasting. I didn't drop to 2 bars until 66.6 total miles into the trip (about 26.5 miles on the return from Julian) The trip was complete with one bar showing, just before the Low Battery Warning came on.
100% battery charge to 18% charge remaining after 81 miles total.
Distance: 40.55 miles.....return 40.55 miles, total 81.1 miles
Elevation gain / loss: 5189 ft
The trip was a success.