Bulletin d’avalanche

Purcell Mountains

Idaho Panhandle Avalanche Center
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Danger d’avalanche

Sun
Alpin
3 · Marqué
Limite forestière
3 · Marqué
Sous la limite
2 · Modéré
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Périmé — ce bulletin a expiré 5 months ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

Quick changes in the weather have created dangerous conditions, and slab depths will continue to increase with some additional snowfall and elevated winds. A rain crust that developed on Wednesday is creating a slick sliding surface for recent snow to fail on, while upper elevations are harboring deeper and thicker drifts. Build a wide margin around slopes 30 degrees or greater and avoid traveling below steep avalanche paths.

Problèmes avalancheux

  • Storm Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely
    Taille
    1.5–2.5

    Continued heavy snowfall and strong winds are creating reactive storm slabs 2 to 3 feet deep. Over the past two days, the storm has favored the Silver Valley and East Cabinet Mountains, though all zones have received snowfall totals that exceed earlier forecasts. On Sunday, most areas favoring the southern end of the forecast area are expected to receive an additional 6 to 10 inches of snow, with some locations picking up over a foot during the day. As snowfall continues, slab depths will keep increasing.

    Very strong winds over the past 24 to 48 hours have drifted the new snow into deeper, stiffer slabs. Elevated wind speeds on Friday and Saturday have continued to stack fresh snowfall over a variety of snow surface interfaces, creating increasingly complex conditions. Conservative terrain selection and cautious travel are imperative. If you cannot clearly see the terrain above you, consider choosing another place to recreate, as unusual weather patterns can produce unusual and unexpected avalanche behavior. Today, it is recommended to stay out of avalanche terrain and avoid traveling beneath avalanche-prone slopes.

    An annotated photo of slab hardness and test results in a wind-drifted area on a north-facing slope around 5,700 feet. Slab depths have increased since this photo was taken. West Cabinet Mountains. 

    March 11, 2026.

    Photo: Chris Bilbrey

  • Persistent Slabs

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

    A cohesive slab 3 to 5 feet thick overlies two buried surface hoar layers, with slab depths continuing to increase during the current storm. One surface hoar layer was buried at the end of January (1/28), and the other in mid-February around Valentine’s Day (2/14). The overlying slab has stiffened and settled due to wind, warmer temperatures, and natural settlement within the snowpack.

    As the slab has strengthened, the likelihood of human-triggered or natural avalanches has decreased. However, persistent weak layers always carry uncertainty, and these layers are currently being tested by rapid loading from the ongoing storm. If one of these layers were to become reactive, the potential remains for large to very large, destructive avalanches with serious consequences.

    Large surface hoar up to 8mm in size is visible to the naked eye at the January 28th interface. This layer is now found 3 to 5 feet below the surface and was exposed here after the overlying slab failed and slid downslope during a propagation saw test.

    March 9, 2026.

    Photo: Jackson George

Avalanche Discussion

Before the strong atmospheric river starts to make its departure out of the region Saturday evening, another round of heavy snowfall will be concentrated primarily in the East Cabinet Mountains and Silver Valley-Bitterroots. These areas have a high chance of receiving 8 inches by the end of the day, and could see close to a foot. The Selkirk and Purcell Mountains will be too far north of the storm track to receive heavy snowfall, but will still get several inches. Storm totals across the region amount to 2 to 3+ feet of snow since March 11.

The Inland Northwest has been under the most potent winter storm we’ve seen so far this season. Aside from just the sheer impressive snowfall amounts, extreme winds, warming temperatures, and shifting rain lines have all contributed to very dangerous conditions building in the mountains. With such rapid change in a short period of time, expect the snowpack to behave in surprising ways.

On Wednesday, the rain line drove higher up in the mountains, resulting in a rain crust fomring right before heavy snowfall. While there is some uncertainty around what exact elevation the rain reached, field teams across the Selkirk, Bitterroot, and East Cabinet Mountains have found this crust to extend around 5,500 feet to 6,000 feet. This crust is acting as a slick sliding surface, and temperature swings have caused the snow above to be inverted and reactive. At elevations above the rain crust, the wind will continue to create deeper slabs.

Poor visibility has made it difficult for field teams to observe the extent of natural releases across the region. Until the weather dies down and the snowpack can settle, avoid traveling in and around avalanche terrain. Large to very large avalanches can release naturally and run long distances in runout zones. Avoid travelling below avalanche paths. If you get out in the mountains, make a well-known plan that avoids slopes over 30 degrees and poses no overhead hazard.  

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