If you think you might be taking a few headers, considering wearing a long-sleeved shirt. The Jackson area experiences frequent high-pressure, sunny days at this time of year.
Temperatures drop rapidly when the sun goes behind clouds and at the end of the day.
Don't forget to have extra layers of clothing available to add as needed. If you are from a significantly lower altitude than the Jackson area, you will probably experience some degree of altitude sickness, especially if you are exerting yourself by skiing and constantly gaining and losing elevation during the day.