Why is the shade so fast?

Utah's snow is the best in the world; both lighter and dryer; at least, during winter. Under a warm spring sun, it becomes a far different animal. Could it be its low humidity contents, or our location under the 40th parallel under which the sun rays hit flatter portions of the slope more vertically, those, by the way, where the problems lies? With this in mind, what I wanted to talk about is what seems to me the huge speed difference that can be observed between the shady and sunny areas on these gentle slopes on a sunny, spring ski day. Sticking to them makes huge difference between moving reasonably and standing still, and I must say that this is a powerful phenom that I had never observed in the northern Alps where that “in-between” stage between decent snow and slush doesn't seem to happen as much as it does under our latitude.

Suffice to say that spring snow has little in common with the real “corn” found in Europe. Here, it seems to be that the old snow granulation is significantly thinner than in the alps and doesn't glide as well; the bottom line is that it's not nearly as good or fun as what's found in the old country (you can't always win, right?) There's also that “scratchy” feeling that one can sense on snow that is about to reach that critical stage and turn “bad” as it keeps on slowing a skier down in quite an unpleasant way.

I've tried to research the subject, but have found no answers to my questions. Until I do, I'll keep to the shady side of the slope...