if you are just starting to explore Powder skiing , I'd look for something wide and soft with Deep rocker profiles ( As Ken mentioned above). This type of ski will allow you to more easily learn the art of skiing the deep stuff - They will provide the float you need and turns are easily initiated.
for reference, I'm 5'10 - 190lbs
Powder skis I have been riding the last 5 winters:
183 Faction Royale - 122mm waist
185 Line Mr Pollard Opus - 118
185 Armada JJ's - 118
184 Salomon Rocker 2 - 122
180 Armada Magic J - 125
A ski with a 98 waist is NOT going to cut it in the Utah Fluff! those are groomer skis out here . After skiing over 200 days in the Cottonwoods the last 5 winters I can assure you that you will want something with a waist over 110mm. That may sound like a big ski but it's all relative.
And don't think they are only for deep days, my daily driver this year has a waist of 112.
4" at Alta can be a magical day on the right ski .