realskiers

Hey Perry -- we had similar dumps in Utah in Feb.  My Supershape Speeds, which are only slightly narrower than your Mags, were just not wide enough (however, they are shorter than your Mags, and I'm heavier, I think -- 225 -- so take that into account).  They were exhausting in the soft snow on the groomed runs, and impossible in powder (didn't even go there).  Rented wider skis for the rest of the week (80 mm one day, then 88 after that). 

My suggestion -- call ahead to a rental shop and reserve a pair in the width you want and the right length.  I'm doing that for my Alberta trip next week.  Some shops even let you swap skis as many times as you want, so you can try a different pair every day, just for fun.  $35 per day...pretty reasonable.  We did that, and it's a great way to go -- that's how I tried the Mythic Riders before buying a pair.

I would take the Magnums anyway, in case the snow stops falling and the groomers pack things down.  Have fun!!!