Avalanche forecast

Selkirk Mountains

Idaho Panhandle Avalanche Center
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Avalanche danger

Sat
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
1 · Low
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Highlights

The snowpack has consolidated and gained stability since the last significant snowfall. However heavy-wet snow falling on a dry cold snow surface today into tomorrow could tip instability in the upper snowpack. Relatively small near surface avalanches could stepdown into deeper buried facet/crust combos to become a large avalanche. Avalanche danger will increase throughout the day today: slopes that are safe this morning will be riskier this afternoon. As new snow totals increase today it would be prudent to backoff steeper slopes and consequential terrain.

Avalanche problems

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    2

    Over the last 10 days, cohesive storm slabs have formed above a variety of weak snow interfaces and each flavor whether it be a notable hardness change, subtle rain or rime crust, faceted combo, or thin grapple layer is behaving slightly different. Varying sensitivity is likely influenced by the slab stiffness or thickness, but in the end, we have copious amounts of snow teetering above softer snow layers. As you gain elevation, southwest wind during the storm efficiently drifted the new snow into thicker, stiffer slabs. You will encounter deeper drifts on leeward-facing slopes, in cross-loaded gullies, and they are typically identified by a smooth, rounded appearance. Cracking in front of your boards or machine, collapsing, and recent avalanches are telltale signs of unstable snow.

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    2–3

    Faceted grains persist around a couple of older rain crusts, creating a weak and slippery sliding interface two to three feet deep across our forecast zones. Before our current storm, the slab directly above both crusts had settled and strengthened more than the faceted grains surrounding the crust. Where the crust has degraded and is more breakable, we’ve found the facets to be larger and weaker. Increased load from new snow may make these layers more reactive, and it's almost impossible to know how close to the failure edge they sit and wait.

    Be especially cautions traveling near exposed rocks or below cliffs where it may be easier to impact weaker snow below. Recent avalanche activity suggest storm slabs in motion can provoke deeper layers to fail resulting in a more dangerous avalanche. Persistent Slab avalanches can behave in surprising ways and span adjacent terrain features, so treat steeper terrain suspect till proven otherwise.

Avalanche Discussion

New snow over the weekend capped off an impressive storm cycle, that delivered copious amounts of much needed snow to all mountain regions. Now that we have had a short break in the weather the snowpack has settled and strengthened. Despite this a degree of uncertainty lingers as sensitivity of crusts, mid-storm density changes and subtle grapple layers persist. Higher elevation areas are where the wind deposited snow has formed into deeper or stiffer slabs and are where larger avalanches are more likely.

However, today into tomorrow heavy-wet snow falling on a soft-cold snow surface could be the load needed to tip lingering instabilities in the upper snowpack into avalanches, which could in turn step down to deeper buried facet crust combos. The crux of backcountry travel today is that slopes that are safe this morning will be riskier to travel upon this afternoon as snow totals increase.

If you are heading into the backcountry today, be prepared to dial it back to more conservative terrain choices this afternoon as the risk of avalanches increases. To account for the uncertainty around deeper weak layer sensitivities, choose low-consequence terrain and give bigger terrain an extra buffer if traveling below.

Interestingly, an IPAC team observed a glide crack yesterday that had opened on an east facing slope in the St. Regis Basin that has produced large avalanches in the past. This appears like an anomaly, but please submit an observation if you find one of these as you are out and about. Glide cracks are known to spontaneously avalanche, so do not travel on or below if you find one.  

Looking ahead, expect avalanche danger to increase tomorrow and possibly Sunday with the possibility of an additional foot of new snowfall totals and possible rain with a rising snowline.

Regions covered