Persistent Slabs
- Hochgebirge
- Waldgrenze
- Unterhalb der Waldgrenze
- Wahrscheinlichkeit
- Very Likely
- Größe
- 2–3
The weak snow that is buried in our snowpack has been pushed to its breaking point. Snowfall intensity peaked overnight and moderate to strong winds picked up early this morning. Winds are drifting the 12-16" of new snow, creating thick wind slabs that are helping to overload the weak snow beneath. These "smaller" slabs will help to trigger much larger slides that fail deeper in the snowpack, producing very large and destructive avalanches.
Today is not the day to try to thread the needle in avalanche terrain. Four human-triggered avalanches were reported in the past five days, before the storm. Persistent slab avalanches fail in ways that surprise even the most experienced backcountry travelers. The combination of an incredibly weak snowpack and an intense storm will produce avalanches that have you second-guessing areas that you once thought were safe. As the skies clear, I'm expecting to see slides that have failed hundreds and hundreds of feet wide, wrapping around terrain features like ridges and gullies, and pulling back into flatter terrain above steeper starting zones. Avalanches may be triggered remotely—from below, above, and to the sides of steep slopes. If you are riding or skiing on a flat valley bottom you may be able to trigger a large avalanche that releases thousands of feet above you and runs down to the valley floor.
There is only one surefire way to avoid this type of problem today: avoid avalanche terrain and terrain that is exposed to avalanche hazard from above.
(1/1/2021) Sun Valley Heli Ski remotely triggered this avalanche from lower angled terrain 800-1000' away. The group felt a collapse that propagated across the bowl into steeper, wind-loaded terrain. Avalanche released on a 9400', E aspect in the Western Smokys. Photo courtesy of Sun Valley Heli Ski.