Bollettino valanghe

Flathead Range & Glacier NP

Flathead Avalanche Center
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Pericolo valanghe

Sun
Alta quota
3 · Marcato
Limite del bosco
3 · Marcato
Sotto il limite
1 · Debole
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In sintesi

Dangerous avalanche conditions persist as continued precipitation, strong winds, and warming temperatures test an already weak snowpack. Even a relatively small slide in the recent snow could trigger deeper weak layers buried 1–5 feet down, producing large and destructive avalanches. Give all steep slopes and their runouts a wide margin.

Problemi valanghivi

  • Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    2–3

    Buried weak layers have been producing large to very large avalanches for over a month, many of them remotely triggered. Several have snapped mature trees, and some have broken back into very low-angle terrain. These layers are lurking about 1–5 feet below the surface, depending on elevation and exposure. The takeaway: in much of the terrain, weak layers sit squarely in the bullseye for human triggering.

    Before the recent storm, these avalanches were becoming slightly harder to trigger, but recent precipitation has added a substantial new load. With more precipitation and wind expected today, the stress test continues, and these fragile layers have shown little ability to handle additional weight. While we can’t rule out natural avalanches, the biggest concern is a human trigger, especially from thin spots such as rocky outcrops, scoured patches, or the bases of trees.

    Obvious warning signs like cracking or collapsing may appear—but they might not. With continued loading, poor structure, and high consequences, the safest approach is to avoid steep slopes—large or small—and give avalanche paths and their runouts plenty of space.

    (3/5/2026)

    A view of the flank of a very large (D3) avalanche remotely triggered on February 21. The slide failed on the preserved surface hoar layer from the January drought.

    Photo: Mark Dundas

  • Storm Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1–2

    Above the rain/snow line, 5–18" of heavy, dense snow fell over the past 72 hours. While avalanches in the recent snow may be a bit more stubborn today, a fresh round of wind and snow could increase reactivity near the surface. Avalanches will increase in size and become more dangerous with elevation, especially in wind-loaded start zones near ridgelines and saddles. On shaded slopes, avalanches in the new snow could step down to a buried weak layer, producing a much larger slide.

    If you head to southwest or west-facing slopes to avoid the persistent slab problem, keep new snow avalanches on your radar. Feel for hard-over-soft layering, look for blowing snow, and watch for any shooting cracks from your feet or machine; default to lower-angle terrain if you see signs of instability.

    Wet Snow AvalanchesThe rain/snow line will rise today, and some incoming precipitation may fall as rain. Amounts look light, and much of the snowpack below 6000’ has already seen a healthy dose of rain over the past few days, so we don’t expect a widespread wet avalanche problem to develop.

    That said, if you encounter rain falling on previously dry snow, it’s time to move off steep slopes and out of runouts, as wet avalanches can develop quickly.

    (4/7/2024)

    This is a soft slab avalanche that failed in the storm snow in a previous season. This is one type of slide that riders could trigger today in areas favored by recent snowfall.

    Photo: Jeff Metsky

Avalanche Discussion

The incremental loading machine has been at work, and totals are adding up. Outside the Swan (3” SWE in 3 days), the Whitefish and Flathead Ranges have nickled and dimed themselves into over 1.5” SWE in the past 3 days. We don’t know how this all played out due to limited observations, but Guy saw a very large natural avalanche Thursday on Nyack in the Flathead Range; another natural was reported near Mount Vaught in GNP yesterday; and most snow pits reveal alarming structure and propagating results. More precipitation is falling now, and temperatures are climbing once again.

Before this storm, the persistent slab problem had entered a quieter, uncertain phase—but slopes facing NW–NE–SE remained dangerous. Last week alone, four large to very large remotely triggered avalanches highlighted the snowpack’s instability. With the current loading, it’s unclear if perceived gains in stability are holding or if we are headed back into an active phase.

The bottom line: this snowpack is untrustworthy. Persistent slab avalanches are most likely during periods of loading, and loading we are. Natural avalanches may happen; they may not. Some folks may get away with pushing into avalanche terrain; others may not. Anywhere this structure exists (slab over surface hoar/facets on a crust), a large and deadly avalanche is possible—and every pit I’ve dug on shaded slopes above 6000’ in the past month has shown evidence of this problem.

Discipline and patience are the practice. Safe and good snow exists in low-angle terrain without steep slopes overhead. We may get out of this at some point this season, but it’s not going to be for the next week plus.

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