Hard and slick snow surfaces are easy to find in avalanche terrain today. It may be possible to trigger a small avalanche in wind-protected areas where new snow has collected and formed slabs. Triggering even a small avalanche has an increased risk today because of the potential for a long-sliding-fall on steep, slippery slopes.
Small wind slabs may exist in isolated areas of lee terrain. The slabs may be reactive to a human trigger, resting on an icy melt/freeze crust and are easily identified in contrast to the hard, textured refrozen snow that now dominates the upper snowpack.
A widespread melt/freeze and rain crust sandwich has formed in the upper 8-12 inches of the snowpack in the wake of Thursday night’s rain event. This crust will likely act as the bed surface for future avalanche activity from developing wind slabs or other snow events. Any new snow that is resting on this layer will have a dramatic difference in snow hardness and can be easily assessed with quick field tests such as a hand shear or shovel shear. In steep terrain, this hard snow surface makes for efficient climbing with crampons, but in the trees and on lower angle slopes this snow surface is less supportable for walking.
It is possible to find new wind slabs from yesterday’s 2 inches of light density snow, but in most areas the snow has likely blown low into the forested valleys and across the border to Maine. Look out for terrain features on lee aspects that offer shelter to the snow below, as this is the most likely place to find enough new snow to trigger an avalanche today.
Forecasters observed some wet avalanche activity from the rain event on Thursday/Friday in Hillman’s Highway and Dodge’s Drop. Multiple cracks that spanned the width of the gully were observed, where a wet slab avalanche had initiated but did not release out of the surrounding snowpack. A blowout of the streambed was observed at a constriction point low down in the Hillman’s Highway path where pressure from water flowing underneath the snowpack built up enough to explode out of the snowpack. Impressively, large chunks of debris and ice were found hundreds of feet away, clearly having traveled through the air. It was a great reminder of the unpredictability of significant rain falling in avalanche terrain and had us wondering how close some other areas were to similar outcomes.
Thanks to everyone who has taken time to submit observations of snow and avalanche conditions, both inside and outside our avalanche forecast area. Please keep them coming.
The Lion Head Summer Trail is now closed for the season due to avalanche risk. The Lion Head Winter Route is open.
