Observations of snowpack ripening in the Sierra Nevada, California, USA

The transition from a dry, sub-freezing snow cover to isothermal snow freel y conducting water was observed near timberline in the Sierra Nevada, Calif ornia, U.S.A. Although there were few major stratigraphic boundaries in the snowpacks observed, minor textural discontinuities were sufficient to both route water laterally downslope and later create ice layers at these strat a. During the first few days of snowmelt, downslope movement of water paral lel to the strata allowed water to bypass lower layers of the snow cover on slopes and converge in microtopographic depressions on level terrain, crea ting isolated drains through the snowpack. In addition to these drains, flo w fingers associated with holes in the ice sheets delivered water to the ba se of the snow several days prior to the thorough wetting of the snowpack. Formation of a series of ice ice lenses just below the snow surface every n ight released much more latent heat than did ice-layer development within t he bulk of the snowpack or at its base.