Bulletin d’avalanche

Selkirk Mountains

Idaho Panhandle Avalanche Center
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Danger d’avalanche

Sun
Alpin
2 · Modéré
Limite forestière
2 · Modéré
Sous la limite
2 · Modéré
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Périmé — ce bulletin a expiré last year. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

A weak snow structure, combined with rapidly warming conditions, will create variability in both snowpack and stability. Expect to encounter a range of snow surface conditions across different aspects and elevations. To minimize avalanche risk, carefully manage your route by avoiding slopes with a saturated snow surface.

Problèmes avalancheux

  • Wind Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    1–2

    Earlier this week strong winds transported recent snowfall, forming fresh wind slabs on north- and east-facing slopes, particularly above treeline and near ridgelines. These slabs are resting on a mix of firm surfaces and weaker snow layers, making them prone to triggering under the weight of a skier or rider. Wind-loaded slopes may appear smooth and pillowed, with cracking or hollow sounds indicating instability. As winds continue to redistribute snow, expect these slabs to become more reactive, especially on steep, leeward terrain. Travelers should carefully assess slope aspect and loading patterns, avoiding wind-loaded features where instability is present.

  • Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    2–3

    The upper snowpack is undergoing rapid changes, with surface hoar, faceted grains, and faceted rain crusts contributing to instability at depths of two to three feet. Snowpack tests conducted near and above the treeline continue to indicate failures within these weak layers. Surface hoar remains prevalent on north- to east-facing slopes, while southeast- to west-facing aspects feature faceted grains or a fragile crust with facets both above and below. Additionally, rainfall from earlier this past week has exacerbated instability by creating a weak interface in certain areas. With ongoing shifts in conditions and significant variability across terrain, uncertainty persists. As the snowpack continues to settle, warm, and evolve, it will undergo cycles of strengthening and weakening. To navigate these uncertain conditions safely, carefully evaluate surface conditions and weak layers before entering avalanche terrain.

    (2/27/2025)

    Believe it or not, but these surface hoar feathers still exist under an over meter deep slab on a northeast-facing slope around 6,100 feet. They got buried on January 31. These grains did not fail in standard snowpack tests, but did fail in a Deep Tap test at 20 taps. Bitterroot Mountains. February 27, 2025.

    Photo: Chris Bilbrey

  • Wet Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    1–2

    Saturated snow in the upper snowpack, combined with direct sunlight and unseasonably warm temperatures, continues to elevate the risk of wet snow avalanches on slopes steeper than 30 degrees. Loose wet snow avalanches have the potential to travel long distances, entraining additional snow and creating hazardous debris deposits at the base of slopes, within gullies, and in creek bottoms. In some cases, wet avalanches may fail as cohesive slabs, which are particularly dangerous due to their size, speed, and the difficulty of escape. These slab avalanches can release suddenly, carrying significant mass and energy downslope, posing a risk to backcountry travelers.  Moisture will likely continue to percolate through the snowpack, further weakening buried interfaces and crust layers. This process is particularly concerning at elevations around 5,500 feet and lower, where temperatures remain well above seasonal averages, preventing the snowpack from refreezing overnight and leading to prolonged instability.

    To minimize the risk of triggering a wet snow avalanche, careful consideration of both elevation and aspect is essential. Slopes that have reached afully saturated snow surface should be avoided, both as a travel route and from below, as wet slides can initiate naturally or from minimal additional loading. Key indicators of instability include soft, wet snow, pinwheeling snowballs, and deep, unsupportive, or punchy snow, all of which suggest that the snowpack has absorbed excessive moisture and is at a critical saturation threshold. Monitoring these warning signs and adjusting terrain choices accordingly is crucial for safe travel in avalanche-prone areas.

    **The presence of fresh glide cracks or widening older cracks is a clear indicator of instability, and slopes exhibiting these features should be avoided. Given the unpredictable nature of glide avalanches, which can release without warning, exercising caution and avoiding travel on or beneath these slopes is strongly advised**

    (2/27/2025)

    Sunny slopes got wet from today's warmup. This large rollerball is the product of us digging out the snowpack and entraining more snow rolling down hill. Blocks of snow this size can knock you over and push you around - especially where more snow volume accompanies. Bitterroot Mountains. February 27, 2025.

    Photo: Chris Bilbrey

Avalanche Discussion

Today may feel more like April, but it’s important to remember that it’s still February. While the diurnal cycle is at play today and throughout the weekend, the snowpack has not yet undergone the typical metamorphosis associated with spring. This first significant warm-up above freezing is causing the snowpack to actively change, which raises classic avalanche red flags. In the past 24 hours, additional red flags have emerged, including shooting cracks and strong winds drifting snow.

 A complex mix of avalanche problems exists at all elevations and aspects. Subtle differences between forecast zones are evident, with the Silver Valley being slightly warmer and further along in the snow’s metamorphosis. At lower elevations, rain has soaked into the snowpack, contributing to complex layering that persists at higher elevations. Our concerns regarding the January Drought Layer (JDL) remain, despite it appearing more stubborn. Surface hoar is still intact, and test results continue to raise concerns, particularly when assessing exposure to consequential terrain.

If you’re heading into the mountains today, don’t let the beautiful weather cloud your judgment. Be aware of the complex range of avalanche issues present. The Persistent Weak Layers tied to the JDL are becoming deeper and more stubborn, but they remain a concern, especially on shaded, non-solar aspects. As temperatures rise into the 40s, surface conditions on sun-exposed slopes will change significantly. When you start to see 6 inches of soft surface snow and observe signs of wet snow problems, such as roller balls or snow sticking to skis, it’s time to move to shadier aspects or lower-angle slopes. If you’re considering venturing into steeper north-facing terrain, it’s critical to dig in and investigate thoroughly. Assess the risks of a potentially low-probability, but large, avalanche before committing to these slopes. Stay alert and make informed decisions.

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