Avalanche forecast

Silver Valley & Bitterroot Mountains

Idaho Panhandle Avalanche Center
View on map

Avalanche danger

Sat
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
1 · Low
Open full map
Out of date — this forecast expired 2 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

Although persistent weak layers, buried two or more feet deep, are becoming increasingly stubborn and harder to trigger, the recipe for a large and destructive avalanche continues to exist. As the overlying slab continues to strengthen, areas of shallow snowpack, such as around rocks, cliffs or tree islands, and convexities, are the most likely places to initiate avalanche propagation into deeper snowpack on open slopes. If you choose to enter avalanche terrain, continue to utilize good travel practices: choose safe zones to stop and regroup, one at a time on or under avalanchable slopes, eyes on your partner, and be aware of your proximity to terrain traps.

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    2

    Weak grains buried 2-3 feet deep are causing instability in the upper snowpack. Slopes near the tree line down to 5,000 feet remain the most reactive. Fragile surface hoar is most common on north and east-facing slopes, while sunnier aspects have growing facets above the crust due to cold temperatures. Although deeper grains are slowly strengthening, stabilization remains slow. Even areas without surface hoar or a faceted crust continue to show signs of instability. Weak layers vary by aspect but all present a risk. With the slab depth above these layers, triggering an avalanche could lead to a large, potentially problematic slide. Backcountry users continue to report warning signs like collapsing and cracking, though avalanche reports have decreased over the past five days. Across all forecast zones, the avalanche problem remains similar, but slab depth influences slide size. The Selkirks and West Cabinet Mountains received more snowfall, resulting in a thicker slab and larger avalanches.

    Surface hoar buried 1 to 3 feet below the surface is just one of the persistant weak layers that continue to cause us concern. Photo: Izzy Davis

Avalanche Discussion

Persistent weak layers from the end of January that are buried two feet, or more, below the surface are becoming increasingly stubborn and hard to trigger. However, that does not mean they have gone away and you get to forget about them. The potential for a large and deadly avalanche still exists if the right trigger point is activated.

Although we have not seen recent natural or human triggered avalanches, red flags such as propagation in pit tests and sudden collapses, continue to be observed. With only a finite number of observations available we still have uncertainty regarding the distribution and sensitivity of the persistent weak layers. What we do know for certain is that the poor structure of the snowpack that could lead to a large and destructive avalanche continues to exist. The problem with persistent weak layers is that they can lay dormant beneath the snow surface for days, or even weeks, with little of no feedback. Remote triggering a large avalanche from shallow snowpack is an increasingly low likelihood, but high consequence, possibility. Overlaying slab depth favors larger potential avalanches in the Selkirks and West Cabs, although 1 to 2’ slabs in the Silver Valley/ Bitterroot zone are still large enough to be deadly.

If you choose to venture into consequential avalanche terrain use good travel practices to lessen your group’s exposure: choose safe zones to stop and regroup, one at a time on or under avalanchable slopes, eyes on your partner, and be aware of your proximity to terrain traps.

Today we will see the first snowfall of an extended active weather period. While new snow does not drive our avalanche problem today, it’s worth paying attention to surface instabilities while you are out and about today. This round of snow is likely warmer than the snow it is falling on and will set up stiffer than underlying cold dry snow. Last night’s snow totals favored Lookout over other areas, with snow totals that could approach 10” by closing time today.

 

**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.**

Regions covered