Bollettino valanghe

Flathead Range & Glacier NP

Flathead Avalanche Center
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Pericolo valanghe

Sat
Alta quota
3 · Marcato
Limite del bosco
2 · Moderato
Sotto il limite
2 · Moderato
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In sintesi

Dangerous avalanche conditions persist at upper elevations. Natural avalanche activity winds down as precipitation wanes and temperatures drop. Human triggered slides, which can be large enough to bury you and entrain a lot of wet debris, remain likely. Simple, low-angled terrain is the easiest way to reduce your risk until the hazard decreases.

Problemi valanghivi

  • Storm Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Likely
    Dimensione
    1–3

    2 to 3 feet of dense storm snow has fallen above about 7000 feet since 2/28. The rain/snow line has dropped over the past 24 hours, with up to 8 inches of new snow above about 5000 feet since Thursday morning. Snow will continue to fall at all elevations through Friday morning. As snowfall wanes, natural avalanche activity will too. However, riders can still trigger slabs of recent snow that will increase in size at upper elevations. This storm has been a prolonged and unusual loading event. Expect avalanches that can break wide and entrain lots of wet debris on their way down the slope. Avoiding slopes steeper than about 35 degrees, with an eye to what’s above you, is the safest way to return to the mountains.

    (2/28/2022)

    A soft soft slab intentionally triggered in the southern Whitefish Range. Additional snow has fallen since the event, making the potential size of triggered slides larger. 

    Photo: Dundas

  • Persistent Slabs

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

    On isolated slopes, dense avalanche debris may release slabs that break on crusts or weak snow buried well below the snow surface. Water has penetrated the snowpack to weak layers buried in January or February. Avalanches that break on or step down to those layers can be much wider, break around terrain features and into multiple start zones. Avoiding slopes steeper than about 35 degrees is the most reliable way of reducing your exposure to this relatively isolated hazard.

    (3/3/2022)

    The top meter of the snowpack near the tail end of the substantial wet, warm storm. Rain late in the storm left wet surface conditions. Warm, dense snow earlier in the storm left moist snow. Below a crust 18 inches below the surface, the snow remains dry.

    Photo: Clancy Nelson

Avalanche Discussion

Since Sunday night, we’ve received 4 to 6 inches of water. It mainly fell as rain below about 6500 feet, which wet the snowpack down to old crusts, weak layers, and windboard from mid-February. Consistent above-freezing temperatures and rain made wet loose avalanches the primary problem near the rain/snow line. Natural wet snow avalanches ran to valley bottoms throughout the storm. Thursday, explosives and skiers triggered small to large wet loose avalanches, and a few more ran naturally in southern Glacier Park, all between 5500 and 6800 feet. Freezing levels finally came down to about 5000 feet by Thursday afternoon.

You’ll notice that all of that information comes from below 6500 feet. Above that elevation, we have more uncertainty. At least 2 to 3 feet of snow accumulated at upper elevations, and though showers taper off this morning, the loading has been near-constant since February 28th. Early this morning, Noisy Basin reports another 1.7 inches of water, and Flattop Mountain in Glacier Park shows another inch. 

So, the danger is trending down along with decreasing precipitation and falling temperatures, though it will still be possible to trigger very large avalanches the higher you climb. Slabs of recent, dense storm snow will have lots of wet mush to entrain. Continue to be wary of avalanches running long distances. 

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