Persistent Slabs
- Alpine
- Treeline
- Below treeline
- Likelihood
- Very Likely
- Size
- 2–3
Yesterday near Galena Summit, Ethan and his partners saw conditions that were "as bad as [we've] witnessed." They remotely triggered avalanches (see video and photos below), experienced near constant snowpack collapsing, and saw slopes that had cracked like panes of glass during the storm. Monday, Ben remotely triggered an avalanche from 1/4 mile away (video). Yesterday, an oberver reported extensive rumbling collapses in shady terrain near Galena Summit. During the storm, the Sun Valley Ski Patrol was able to ski trigger small avalanches on some steep road cuts and shady slopes while getting terrain ready to open to the public.
All slopes that had snow on the ground before the recent storm are extremely suspect. This includes most aspects at upper elevations, and shadier NW-N-NE-E aspects at middle elevations. It will take time (weeks/months?) for the weak, faceted layers and crust+facet combinations to fully adjust to the huge load from this storm.
How should we travel? VERY CAREFULLY. Stay off of and out from beneath steep slopes where old snow existed before this storm. Conditions change quickly as you move up in elevation and to shadier aspects; safely traveling in or near middle or upper elevation avalanche terrain today will require a cautious attitude, expertise, and near-constant vigilance to avoid slopes with old, weak snow beneath the storm snow. You can significantly reduce the chances of getting caught in an avalanche by sticking to terrain free from wind-effects where the storm snow fell on dirt or bare ground.