Terms for subject Geography containing permanent snow

English	Russian
number of days without permanent snow cover	число дней отсутствия устойчивого снежного покрова (As the number of days without permanent snow cover increased, the proportion of white weasels dropped precipitously – by Ben Guarino, The Washington Post Tamerlane)
permanent snow	вечные снега
permanent snow stretch	снежник-перелеток