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

Human-triggered avalanches are likely today, especially where wind is drifting snow onto open slopes near ridgelines. You could trigger a dangerous slide remotely from lower-angle terrain above, below, or adjacent to a steep slope. Enjoy the new snow safely by sticking to low-angle runs without overhead hazard, or seek out typically sunny slopes where a stout, supportable crust exists in the upper snowpack.

Expect loose snow sluffs on steep solar slopes. Most should be small, but they could still be problematic if they knock you off balance in steep or exposed terrain.

Problemi valanghivi

  • Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Likely
    Dimensione
    1.5–2

    A reactive layer of buried surface hoar will be tested this weekend, and we’re confident it won’t pass. Human-triggered avalanches will be easy to initiate on steep slopes, especially where wind is actively loading. Look for blowing snow to identify these areas. In addition, we can’t rule out a natural avalanche or two, particularly in upper-elevation start zones where snowfall stacks up on the higher end of the forecast.

    The weak layer is buried 6”–2’ deep (and getting deeper) and is widespread to the ridgeline. It has already produced six human-triggered avalanches, including one remotely triggered on Thursday, and has shown no signs of strengthening since its burial over two weeks ago. Assume it exists on any steep, open slope without a stout crust under the recent snow.

    So far, a thin, soft slab has kept avalanches relatively small — but we know what this layer can do with a stiffer slab (see the 1,000-foot-wide slide on Snowshed). That process starts today, as wind will stiffen and thicken the slab — even a few inches of new snow can quickly drift into a foot-thick slab that rests precariously on this house of cards.

    Avoid steep, shaded slopes — both open and lightly treed — and stay alert in connected lower-angle terrain where a slide from above could reach you.

    (2/12/2026)

    Riders remotely triggered this slab avalanche on Thursday from a nearby ridge. This slide failed on a buried layer of surface hoar 40cm below the surface. This weekend's snowfall may result in natural avalanches on this weak layer and make human-triggering likely. This slide occurred on a NE slope at 6800'.

Avalanche Discussion

Avalanche danger will rise as we move forward, with the snowpack reactive to the weight of a human or machine today, tomorrow, and into next week. During this time, avalanche size will increase, and I anticipate a natural cycle at some point, though it may not occur this weekend.

We enter this period with a widespread, reactive weak layer that is still avalanching and collapsing weeks after burial. Remote triggers are common, and even relatively low-angle start zones — such as the ~30° slope at Tunnel — can fail. Any previous margin for nibbling around the edges will vanish as the load builds.

Absence of Wind Slab Problem? 

As it happens, shaded slopes where the persistent slab lives are lee to this southwest flow. By avoiding the persistent slab, you will also avoid the wind slab.

New crop of surface hoar:

We will have to dig beneath the new snow to see if the most recent layer of surface hoar formed over the past few days was preserved and, if so, on which aspect. It’s somewhat immaterial to the problem on shaded slopes right now, but it could be something on sunnier windward slopes if it were buried intact. I don’t expect slab formation yet on those slopes with today’s cool temps and right-side-up snowfall, but we (and you!) can investigate this potential.

Good riding conditions:

On a brighter note, dust-on-crust conditions on sunny slopes with a stout underlying crust should provide enjoyable, manageable riding — just confirm the crust is present and supportive, and stay aware of sluffs. Low-angle shaded slopes should ride well, too!

Regioni coperte