Turnagain Pass

Sunday afternoon through Tuesday evening brought a warm and windy storm to the core advisory area scouring many ridges of snow, and building dense wind slabs on leeward slopes.  With ridge top winds predominantly from the East, expect West-facing slopes, particularly in the alpine to have that dense, pillowy look, indicative of wind slab (see photo below).  The steeper the terrain today, the more likely you will be to find and trigger a wind slab.  Likely trigger points include areas where the slab thins or near rock outcroppings.  It’s important to keep in mind when dealing with this avalanche problem that wind slabs are notorious for luring skiers well onto a slope before failing, often times above a skier. 

At treeline elevations winds were quite erratic during this storm so expect wind slabs to have formed on a variety of aspects.  It’ll be time well spent today to seek out small test slopes (with zero consequences) on your skin up toward alpine and jump on these hollow-sounding slopes to see how the snow reacts to a skier’s weight.

All signs are pointing toward a storm layer that will stabilize relatively quickly but as always, it’ll be prudent to pay attention to any red flags the snowpack is giving us and practice safe travel protocol both on the ascent and decent today.

Notice the difference in texture between a wind-scoured ridge (safer travel option) and a wind-loaded slope where the slab exists.

Though it’s been a full two weeks since we saw peak avalanche activity on a buried surface hoar layer in the Turnagain zone, it’s still proving reactive in snow pit tests.  This last storm added significant weight to these weak layers where wind slabs formed (though not uniform across the landscape), but judging by the lack of natural avalanche activity yesterday it doesn’t appear to have definitively tipped the stress vs. strength balance. Currently dormant in terms of avalanches, the nature of a persistent weak layer is such that it can return to a state of activity as more stress (weight) is added and thus we’ll continue to track and test these buried weaknesses as we ski into a new year.