Once snow has accumulated on the landscape, the individual snowflakes and ice grains can be rapidly transformed or metamorphosed into a structured snowpack. Metamorphism ultimately influences the thermal conductivity and liquid permeability of the snowpack that in turn influence the snowpack temperature regime and storage and release of liquid water. Snowpacks vary seasonally from low density, sub-freezing snowpacks capable of refreezing any liquid water inputs to isothermal, dense snowpacks that rapidly transmit liquid water to the ground below. In this chapter, important processes controlling snowpack metamorphism and the conduction of heat and liquid water in snow are described along with methods hydrologists use to describe snowpack condition.