Bollettino valanghe

Flathead Range & Glacier NP

Flathead Avalanche Center
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Pericolo valanghe

Fri
Alta quota
2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
2 · Moderato
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Non aggiornato — questo bollettino è scaduto last year. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

Warming temperatures will make avalanches more likely throughout the day. Wet snow may sluff easily and could trigger larger avalanches on buried weak layers. Mushy surface snow and roller balls are signals to move off of and out from under steep slopes. 

Problemi valanghivi

  • Persistent Slabs

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

    It is still possible to trigger a large avalanche on slopes that haven't already released down to buried weak layers. It's not clear how sensitive these layers are to human triggering after last weekend's storm.  Slabs will be thicker and more sensitive where you see blowing snow or wind-affected surfaces. Warming may increase sensitivity throughout the day. Take a cautious approach: plan on digging and testing with large columns to determine if a persistent slab structure remains intact and reative.

    Slides that release on these layers can break surprisingly wide and connect across terrain features. Pick routes that minimize your time under steep start zones that haven't avalanched.  Step back to simple terrain if you get propagation or collapses. 

    (2/24/2025) 

    A very large avalanche in the Flathead Range. Warming temperatures will increase the likelihood of large avalanches on slopes that remain intact following last weekend's Atmospheric River. 

     Photo: Jackson George

  • Loose Wet

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1.5–2.5

    The hazard of triggered and natural wet snow avalanches will increase as temperatures warm. Even small slides could have outsized consequences above terrain traps or if they trigger a larger avalanche on buried weak layer. 

    Rollerballs fanning down a slope are a sign of developing wet snow hazards and a prompt to move to shadier or less steep slopes. Avoid sidehilling steep gully walls if you or your snowmachine are sinking more than a few inches into soft, wet snow. The dense, heavy debris involved in these slides is difficult to escape and can result in deep burials on short slopes. 

    (12/2/2024) 

    Rollerballs, pinwheels, and small point releases are all signs that the surface is ripe for wet loose avalanches.  Move to less steep terrain or slopes where the snow is still dry. 

     Photo: Jackson George

Avalanche Discussion

The weather has turned spring-like following last weekend's Atmospheric River. However, we've got a long way to go before we can enjoy a predictable spring snowpack. Complexity and uncertainty remain high following our last storm. Don't let pleasant temperatures and sunshine lure you on to steep slopes without a little critical thinking. Keep in mind:

  • Weak layers remain untested on slopes where recent large avalanches did not occur.
  • Warm temperatures will start to creep into progressively higher elevations and shadier slopes.
    • Warming can be a stimulus for weak layers.
    • Small to large loose wet avalanches are also effective triggers for larger avalanches on buried weak layers. 

Observations from yesterday included a couple visits to recent avalanches near the Continental Divide (6996, Elk Mountain). These avalanches occurred on wind loaded slopes and involved buried weak layers. This morning we have dropped the Wind Slab problem due to tapering winds over the last two days. Recognize, however, that hard slabs of wind-drifted snow resting on weak layers will be slower to heal and are encompassed in the Persistent Slab problem. 

If you are traveling near the Continental Divide, expect to find freshly formed soft slabs above 6500'.  Steer away from steep slopes with obvious signs of wind effect - like an etched surface or dune-shaped features. Both parties traveling in that area noted that recent Southwesterly winds had drifted in crowns on leeward slopes. 

An observations from the central Whitefish Range cataloged several more large natural avalanches from this weekend. They also noted that an avalanche at Red Meadow Lake was large enough to break the ice around the lake. 

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