Professional Observation

Observation Details

Signs of Unstable Snow

Key Points

I spent a few hours touring around multiple aspects in Bishop Creek thinking about the future. I could still trigger small sluffs too.

• Bishop saw much less snow and wind during the last storm. I found about 2-4 inches of soft (F-hard) recent snow still sluffed easily on very steep slopes. Sluffs were easiest to trigger when there was a hard crust under the new snow. I saw a few small recent natural loose dry avalanches in very steep terrain on Bishop Bowl. With much less wind-affect, recently deposited wind slabs were few and far between, very small, and only cracked under my skis very locally (less than a meter long).
• I checked on solar aspects since it’s supposed to be warmer and even less windy tomorrow. I found the recent snow still dry atop slick hard surfaces underneath on both southeast and southwest aspects. That means that it may transition to wet for the first time if the weather forecast verifies.
• Northerly aspects below about 9500 feet are developing a concerning structure. Under the recent low-density snow there’s a thin, breakable crust with 2mm facets under that. In some wind-sheltered areas, the new snow sits right on the facets. Under the facets is old, hard, wind-packed snow. So right now there’s a bed surface (old wind-packed), a weak layer (well-developed facets), but no slab yet. Above about 9500 feet the facets are still there, but they’re sandwiched between thick and hard wind-packed layers. I’ve been worried about this structure going forward with the possibility of more snow on the horizon. The potential slab over the facets doesn’t have to drop all at once. Often persistent slab problems develop over several loading events until the overlying slab is thick enough and stiff enough to propagate a failure through the weak layer. Food for thought.