Bollettino valanghe

Flathead Range & Glacier NP

Flathead Avalanche Center
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2 · Moderato
Limite del bosco
2 · Moderato
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

Saturday's rider-triggered slide in the Whitefish Range confirms a sensitive surface slab is developing over buried weak snow. Bypass slopes with dense surface snow in favor of softer conditions and low-angle terrain. Today's warming may develop wet snow avalanches on steep slopes.  

The danger is higher in the Swan Range, where a buried layer of surface hoar is responsible for remotely triggered slides on Friday and Saturday.

Problemi valanghivi

  • Storm Slabs

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

    In many locations, recent snowfall rests on a weak layer (facets or surface hoar) and crusts. Warming temperatures and wind may stiffen this snow into a cohesive slab. These features will be thicker, larger, and more dangerous in wind-drifted areas, although they could also be problematic in sheltered terrain. Slides can be triggered remotely from flat terrain above, to the side, and below steep slopes. This looks to have occurred Saturday in the northern Whitefish Range, where a motorized user triggered a small slab avalanche (See adjacent image).

    Look and feel for dense surface snow where your skis, board, or machine do not sink in as deeply. Cracks beneath you indicate you have found a slab, while cracks shooting away from you indicate a sensitive slab. This is a near-surface problem, and hand pits are a good way to assess how well the recent snow is bonding to the underlying layer.

    Seek out softer snow and low-angle slopes for a safer and more enjoyable experience. You might be more likely to find these conditions on northerly slopes sheltered from the wind. 

    (1/31/2026)  This small soft slab avalanche was triggered by a motorized rider in the northern Whitefish Range on Saturday. This likely failed on the buried weak snow + crust setup. Riders could trigger slides similar to, or larger than, this one today.

  • Loose Wet

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1–1.5

    Friday and Saturday’s warming temperatures moistened the snow surface on many low- and middle-elevation slopes, and, to a lesser extent, upper-elevation terrain. Today will be warmer than the previous two days, increasing the risk of wet avalanches on steep slopes, especially on snow that is becoming wet for the first time. 

    Monitoring surface conditions is a relatively straightforward way to determine whether this problem is developing. If a thin surface crust formed overnight, its breakdown will be one of your first clues. Snow falling from trees indicates warming, with fresh rollerballs a sign that surface snow is weakening and may lead to wet-slide activity.

    If the sun makes an extended appearance, slopes receiving direct sunlight will warm quickly. If you find yourself in mushy snow, move to a shaded aspect or a low-angle slope free of overhead hazards.

    (4/24/2022)

    Natural and human-triggered wet loose slides like this one are possible today. Near-record warmth may wet upper-elevation snow.

    Photo: Mark Dundas

Avalanche Discussion

In the Swan Range, precipitation from earlier this week deposited around 1” of water/10” of snow on an impressive layer of surface hoar first noted by our Creston observer on January 21. See his images of this layer here and here. Josh visited Noisy Basin on Friday and remotely triggered a slab avalanche on this feathery layer (Observation). On Sunday, riders remotely triggered a slab avalanche from a ridgeline near Mt Aeneas. This slide was 150' wide by 6" deep (Observation). The Swan Range remains our primary concern because surface hoar may persist for extended periods, can be remotely triggered, and produce avalanches wider and larger than expected.

The central Whitefish Range picked up roughly the same amount of water as Noisy, with the northern and southern portions of the range picking up around half that amount. Recent observations from the southern Whitefish Range indicate that new snow rests on weak faceted snow surrounding a crust. A motorized observer triggered, possibly remotely, a small soft slab avalanche on Saturday in the northern part of the range (Observation). This slide most likely failed due to the weak-layer + crust setup.

We have had no recent observations from the Flathead Range or southern and central Glacier Park. These areas received the least amount of recent snow.

We are currently experiencing another impressive warming event, with mountain temperatures as of 0400 hovering around freezing. Sunday’s temperatures are expected to flirt with record highs, especially in Kalispell, where 54 F was recorded in 1971. Observers in the southern Whitefish Range on Saturday noted how the warming impacted the surface snow (Observation, Observation).

 

 

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