Selkirk Mountains

Dangerous slabs of snow two feet deep are stressing a complex array of fragile weak snow layers below. As new snow depths have increased, it has become easier to collapse a slope or trigger a large, potentially deadly avalanche from a distance. Triggering an avalanche on a wind-drifted slope is more likely to span adjacent terrain features and run full track into mature forests. Cautious route-finding and conservative decision-making are essential.

Fresh, cohesive slabs teetering above a pile of large (1-1.5 mm) faceted grains and very large surface hoar (15 to 25 mm) is like rolling the dice with a loaded gun. It won’t take much effort to trigger a large, dangerous avalanche on slopes steeper than about 30 degrees. Now that the main loading period is behind us, we move into a more incremental loading pattern. These periods are more challenging to track the slow upward progression of the snowpack sensitivity needle, and often require a higher level of patience and not walking the line with slim safety margins.

Observations from the last few days report reactive borderline touchy conditions – natural avalanches triggered by falling cornice and many running naturally during a moment of high precipitation intensity, snowpack tests failing and/ or propagating during isolation and with easy force, and folks triggering avalanches with long-running cracks from a distance. Most of which is occurring at a well-preserved and upright layer of surface hoar with feathers ranging 15 to 25 mm in size – also sitting on top of a foot of large, faceted grains. With the snowpack providing us with more “free” evidence of dangerous conditions than we’ve seen so far this season, why did so many slopes across our zones not avalanche?

With how weak (mostly F to 4F-) these persistent grains are below the new snow we will likely be stuck at an elevated danger level for some time. We may notice a subtle increase in sensitivity of the slab, weak layer combination as the newly formed slab settles under its own weight, or the stiffening of the slab will help mask the danger looming below. As you move through the mountains, carefully evaluate not only the terrain you’re traveling in, but how close you put yourself to steeper slopes. With the patchwork of old, wind-affected layers and crust, surface hoar and faceted snow now buried, avoiding slopes and convex rolls steeper than 30 degrees might be better than trying to outsmart the sleeping monsters. Avoid travel above terrain traps like gullies or depressions with steeper hazards directly above – especially where you have no fast exit option.

While tough, adjusting our travel mindset from what it was for most of January will go a long way to help reduce your avalanche risk. The usual risk management strategies should not be relied on during times like this. The overall size and weakness of buried persistent grains is nerve-racking and somewhat atypical for what we usually deal with this time of year across North Idaho. Don’t rely on stability tests as a go or no-go decision, and treat early warning signs of fresh avalanches, cracking in the snow, and loud audible collapses as your backcountry guardian angel.

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**We continue to receive intermittent reports of opening glide cracks and some failing naturally producing large to very large glide avalanches. Avoid traveling on or below slopes where a glide crack has opened. These types of avalanches are difficult to forecast when they will release.**