Persistent Slabs
- Alpine
- Treeline
- Below treeline
- Likelihood
- Possible
- Size
- 2–3.5
Large, stubborn slabs several feet thick or more exist over faceted weak layers in the upper snowpack. Remote triggers and natural avalanches failing on these persistent weak layers have been gradually diminishing since widespread activity last week. The most recent persistent slabs have required larger triggers such as the mass of a smaller avalanche running through the terrain or a cornice falling. The greatest number of avalanches have occurred on easterly-facing slopes where faceted crusts exist. Similar structures exist on west-facing terrain, and shallow slopes on the northern half of the compass have also been problematic. Recent warming on lower elevation and more southerly aspects has strengthened the upper snowpack with crusts, and triggering persistent slabs is less likely in that terrain.
Early warning signs for this avalanche problem are rare and feedback is infrequent. You can reduce your chance of triggering this avalanche problem by avoiding recently wind-loaded terrain and unusually shallow terrain. Safer riding is where the snowpack is deep, wind-protected, and on slope angles less than 35 degrees, without steeper slopes above.
Very large persistent slab on the east face of Gothic Mountain. 3/31. This avalanche was likely triggered by a cornice falling onto the slope.
