According to the Western Region Climate Center, the monthly mean snowfall at Alta is:
Thus, climatologically, January is the snowiest month at Alta, although it is hardly different from December, February, or March. There is a dip in February, but keep in mind that there are only 28.25 days in February (on average). If we adjust the February mean for 31 days, as occurs in December, January, and March, the February snowfall normalizes to 82.6", virtually identical to the other months.
Thus, there is no evidence for a mid-winter snowfall minimum at Alta.
Whether or not there is a dip in the frequency of major storms (say 10" or more) requires further analysis. If there is, that would simply mean that there must be an increase in the number of minor storms, or fewer storms of greater intensity, so that the monthly mean remains high. Perhaps someone can look into this.