Surface Hoar

Raven Eye Photography

Snowmobile ski in surface hoar

Surface hoar consists of feathery-shaped frost crystals that grow upward from the snow surface when the air just above is cooled to the dew point.  Once buried, layers of surface hoar are slow to gain strength, sometimes persisting for a month or more as a weak layer. 

Surface hoar grows most easily on cold and relatively clear nights, when the wind is calm, though it can also grow during the day on shady slopes. It can be identified by the feathery, sparkly crystals that grow on the snow surface as it forms.