International Building Code 1608.2
Ground snowloads. The ground snowloads to be used
in determining the design snow loads for roofs shall be determined
in accordance with ASCE 7 or Figure 1608.2 for the
contiguous United States and Table 1608.2 for Alaska.
Site-specific case studies shall be made in areas designated
“CS” in Figure 1608.2. Ground snow loads for sites at elevations
above the limits indicated in Figure 1608.2 and for all
sites within the CS areas shall be approved. Ground snow load
determination for such sites shall be based on an extreme value
statistical analysis of data available in the vicinity of the site
using a value with a 2-percent annual probability of being
exceeded (50-year mean recurrence interval). Snow loads are
zero for Hawaii, except in mountainous regions as approved by
the building official.