Boletín de aludes

Flathead Range & Glacier NP

Flathead Avalanche Center
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Peligro de aludes

Fri
Alta montaña
2 · Moderado
Límite del bosque
2 · Moderado
Bajo el límite
1 · Débil
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Desactualizado: este boletín caducó 2 years ago. Estás viendo condiciones pasadas, no el boletín vigente.

Lo esencial

Change is here. New snow and wind will build fresh slabs on the leeward side of ridgelines. Slabs will grow thicker and become more dangerous throughout the day and overnight. It remains possible to trigger a 2 to 4-foot hard slab that fails on a persistent weak layer. Steer towards lower angled slopes sheltered from the wind. 

Expect the danger to rise to CONSIDERABLE overnight.

Problemas de aludes

  • Wind Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Possible
    Tamaño
    1–2

    New snow and strong southwesterly winds will build slabs on the downwind side of ridgelines and cross-load gullies further downslope. Expect this problem to grow in size and become more dangerous throughout the day with continued snowfall. Shooting cracks and active wind-loading will be clues that this problem is ripe for triggering, and should point you towards terrain sheltered from the wind. A triggered avalanche may propagate wide distances and run further than expected due to the smooth crust new snow is landing on. 

    (2/29/2024)

    Active wind-loading off a cornice on a ridgeline at 6700 feet. Avoid slopes directly beneath areas you see active wind-loading.

    Photo: Mark Dundas

  • Persistent Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Possible
    Tamaño
    2–3

    Weak layers buried 2 to 4 feet down remain a concern in areas where a hard and supportable surface crust does not exist. Currently, it is not clear where that elevation is. North-facing slopes at upper elevations are the most worrisome. The best approach to this problem is to avoid steep, rocky, complex-looking avalanche terrain. Being caught in a 2 to 4-foot hard slab may be unsurvivable. Continue to be patient and conservative with your terrain selection.

    (3/17/2024)

    Key into the terrain where this avalanche released: steep, rocky, varaible snow depths. Many recent slides failed in this type of terrain.

    Hard slab avalanche on Nyack Mountain that failed on a northeast aspect at upper elevations on March 16. This slide likely failed on a layer of facets above the early February crust. 

    Photo: Mark Dundas

  • Loose Dry

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Possible
    Tamaño
    1–1.5

    Expect to be able to trigger sluffs in steep terrain sheltered from the wind. Sluffs will run far and fast due to the underlying smooth crust. These avalanches should be easy to manage but can be consequential if they catch you above terrain traps. If you choose to ride in more consequential terrain, plan your descent to allow your sluff to run next to you, not over you.

    Plan for Wet Loose avalanches where precipitation is falling as rain. This will most likely be below 5000 feet where there is still snow. Watch for rollerballs or point releases on steep cut banks or gullies on your climb up this morning. 

    (2/3/2023)

    An older image of a Loose Dry slide in the top 8-10" of low-density snow resting on a crust. Debris traveled approximately 350 feet. 

    Photo: Mark Dundas

Avalanche Discussion

It is time to put the winter thinking cap back on since snow will fall above roughly 5000 feet. Conditions will be drastically different than the past week.

New snow accumulations will vary throughout the forecast areas. Expect a range between 2 to 6 inches of snow by this evening and an additional 4 to 8 inches by tomorrow morning. Winds are forecast to average in the 20s out of the southwest at upper elevations.

The most dangerous new snow problem to manage is wind-drifted snow. Slabs will build downwind of terrain features and may grow to a size that can bury or injure a human. Keep close tabs on snow accumulations and drifting snow throughout the day. New snow is landing on smooth crusts and weak snow surfaces. This will allow avalanches to run far distances and be easy to trigger. A Dry Loose avalanche problem will exist in terrain sheltered from the wind.

The best riding will exist on slopes sheltered from the wind with moderate slope angles. That's for both safety and quality. If you jump onto steep slopes, you are likely to  sluff off all the new snow, leaving yourself a crusty bed surface to ride. Slopes with moderate or lower slope angles will also be a much safer option when dealing with the Persistent Slab avalanche problem. 

Help avalanche researchers! The Colorado Avalanche Information Center, the Avalanche Research Program at Simon Fraser University, and the U.S. National Science Foundation National Center for Atmospheric Research are researching how skiers, snowmobilers, snowshoers, ice climbers, and anyone else who travels in the backcountry interpret avalanche forecast information. Part of this research includes a specific survey to better understand how useful avalanche forecast information is for trip planning. 

Completing this survey will take approximately 20 minutes. Thank you for sharing your feedback to help us improve avalanche risk communication. 

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