Vail & Summit County

Snowpack

Following Storm #8, and over the weekend, we experienced ideal conditions for the formation of surface hoar at Red Mountain Pass - generally clear skies (until Sunday afternoon), a thick layer of relatively warm new snow (Storm 8) 'exhaling' large amounts of water vapor toward the comparatively very cold snowpack surface (losing heat via radiative cooling, night and day), otherwise high relative humidity, and light winds. Under these conditions, the feathery forms that are familiar along rivers on some winter mornings, 'growing' off trees, will grow off the snowpack surface creating a beautiful, sparkling new layer of tall and thin hoar crystals on top of the snowpack. The attached photo shows a sample of surface hoar, in the shade, near Swamp Angel Study Plot yesterday (Sunday), not long before snow showers likely buried this incredibly delicate structure intact. Depending on how extensive this crop of surface hoar was, and how well it was preserved under new snow and remains sheltered from wind and sun, this layer of surface hoar may prove to be a very important weak layer in the snowpack and be responsible for natural or human triggered avalanches later this season. Surface hoar is implicated in many avalanche accidents in British Columbia, where the climatology is very favorable for its formation, but not quite as often a problem in Colorado. Nonetheless, savvy backcountry skiers and ski patrollers pay very close attention to Colorado surface hoar layers.