An example of the chemical evolution of snowpack associated with its thawing phenomenon was presented. The snowpack was accumulated during an isolated event of snowfall. Bulk snow core was sampled for each occasion with a time interval of several hours, and chemically analyzed. Sea-salt originated species, such as Na+, Mg2+ and Cl-, showed a rapid reduction in concentration with time compared to other species (H+, NO3-, SO42-). The result suggests that sea-salt species can be selectively enriched in snow thaw discharge. Such a behavior may be attributed to the structure of each snowflake, consisting of acid-rich crystal and sea-salt-rich rimed cloud droplets.