It's freakin' Utah, there is always 30" plus of 5% powpow! (24" plus on the Park City side of the Wasatch, but deep nonetheless).
Go fat, something like a pair of Gotamas. Hey, come to think of it, I know a guy who is selling a pair:http://forums.epicski.com/showthread.php?t=17667
In all seriousness, what PM said, look around, I know I've answered this question countless times.
I've skied countless days over the two foot mark, iIn short, your AX3's will be fine. One of the best skiers I know, skis a Rossi XX in most all conditions, including bottomless. You might want to check out something wider and softer, which are around. A word of caution thought, if it looks like it is going to dump, pick up your rentals the day before, as shops have no problems renting that gear on pow days.
On powder cords: Not totally necessary, I've never used them out here, and have never lost a ski (knocking on wood). When you fall and feel a ski pop off, it is usually near the surface. If you must use them, please tuck the things in and don't let them hang from your skis. A quick way to piss off the locals.
If you ever do lose a ski, most patrols I'm familiar with have a metal detector around.
Ohh and another note, fat is not always the best for powder. There I said it. Ski flex also has a lot to do with it, not only stiffness, but where it flexes at.