If your base gets grey and looks velvety the snow has burned the base. It tends to happen more out in the section close to the edge where the bevel is put in
It happens when we have very cold abrasive snow and you had no wax or a soft warm temp wax on the skis. Colder temp waxes are much harder which protects the base.
if You French Fry when you should Pizza you are going to have a bad time