Bollettino valanghe

Swan Range

Flathead Avalanche Center
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Pericolo valanghe

Sat
Alta quota
3 · Marcato
Limite del bosco
3 · Marcato
Sotto il limite
1 · Debole
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Non aggiornato — questo bollettino è scaduto 7 months ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

Dangerous avalanche conditions persist, and large avalanches remain likely on steep slopes. Record warmth, full sun, and a widespread weak layer are a potent combination that warrants a simple, conservative travel plan. Choose low-angle terrain and avoid exposure to avalanche-prone slopes above you.

Problemi valanghivi

  • Persistent Slabs

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

    Large surface hoar (and facets) around a crust are buried up to 1 foot deep in sheltered terrain and 2+ feet deep in wind-loaded areas. Since 1/30, this layer has produced at least six human-triggered avalanches (many remote), a natural cycle in the Flathead, widespread whumphs, shooting cracks, and poor test results. We’ve seen no signs of strengthening, and it exists on all aspects at mid and upper elevations.

    This is not a manageable weak layer—you have to avoid it. Given how widespread it is, that means staying off of and out from under steep slopes, especially where more than 8 inches of snow rests on the weak layer. These conditions are most likely to be found on wind-loaded north- and east-facing slopes. A recent avalanche highlights the danger: a slab just 1 foot deep propagated 1,000 feet across the slope.

    With a stiffer slab, signs of instability such as shooting cracks and whumpfs may become less common. Heed their call, but don’t rely on them. Any steep slope without a supportable surface crust is suspect, and consequences should be carefully considered if you’re traveling on or beneath it.

    Cornices and Ridgelines:

    Nearly 36 hours of above-freezing temperatures at upper elevations make cornice failures possible today, and slides triggered from the ridge could pull back farther than expected.

    (2/3/2026)

    Riders were ascending a northerly-facing slope when they triggered this thin, soft slab in the northern Whitefish Range. This avalanche likely failed on a buried weak layer.

    Photo: Flathead Avalanche Center

  • Loose Wet

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

    Observed wet loose activity has remained limited. Clear skies overnight likely produced a refreeze at all elevations, though strong inversions mean the refreeze will be thinner and weaker at upper elevations. Wet loose avalanches shouldn’t become an issue until these crusted surfaces break down. When they do, sun-exposed slopes will be the primary concern, especially for natural activity.

    Be your own now-caster for this problem. Move off of and out from under steep slopes if you’re sinking past your boot tops, or if you see fresh rollerballs or pinwheels. Pay close attention to terrain above you—steep upper-elevation slopes will soften first and may shed snow even if where you’re standing feels stable.

    Keep in mind that a wet slide could also act as a trigger for a larger, more dangerous avalanche (see Problem 1).

    (2/4/2026)

    Rollerballs, like these, are a sign that wet snow is ready to slide.  Move to lower-angle slopes anywhere you find mushy surface snow. 

    Photo: Flathead Avalanche Center

Avalanche Discussion

Unusual weather = unusual avalanches: keep it simple and safe during these conditions.

First, we buried widespread surface hoar, all the way to ridgeline, seemingly on all aspects, in all three zones. In many places, this surface hoar grew exceptionally large before being capped and preserved. This problem was already producing avalanches before unusual event number two: record warmth, now in its third day. Will the warmup further stress the weak layer or introduce liquid water into the surface hoar, potentially triggering a natural cycle? We don’t know, but it’s possible.

Prior to the warmup, I had seen enough to avoid steep slopes with more than 6-8” of snow above the weak layer. With the warming and the stiffening of the slab, I’m even more uneasy now.

Yesterday, Lydia and I moved cautiously. While we didn’t find obvious red flags, we found surface hoar everywhere we looked, the slab had stiffened, and large column tests propagated easily and repeatedly. Staying off of and out from under steep slopes was an easy call—and it remains a good one today. The upside: we found pseudo-corn on a supportable crust that made for enjoyable low-angle travel.

Surface hoar is very slow to strengthen, and this is one heck of a crop. As we move out of the warmup later this weekend, surface crusts may help to limit where avalanches can fail on this layer. But on shaded slopes at the upper elevations, I suspect we will deal with this problem for a while yet.     

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