15-years of satellite imagery shows snow's comings and goings

Winter snows in the Sierra Nevada Mountains create the snowpacks that serve as a primary water source for the western U.S. Due to rising average temperatures, snowpacks in the Great Basin appear to be transitioning from seasonal (predictable amount and melt rate), to ''ephemeral,'' (short-lived, less predictable). Ephemeral snow has been poorly tracked and understood.