Bollettino valanghe

Whitefish Range

Flathead Avalanche Center
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Pericolo valanghe

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

In sintesi

You can trigger an avalanche on steep slopes where new and wind-drifted snow has formed slabs sensitive to the weight of a rider. Cracking or collapsing under your feet or machine are signs of unstable snow, and suggest you seek out lower-angled terrain. Avoid slopes with overhead hazards like obvious avalanche paths or overhanging cornices. 

The avalanche danger will INCREASE through the night as a strong cold front brings heavy snowfall to the region. 

Problemi valanghivi

  • Wind Slabs

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

    Yesterday's snowfall and southwest winds formed drifts of snow sensitive to human triggers. Gusty southwest winds will continue to drift new snow throughout the day. Blowing snow will point in the direction of freshly forming slabs. You will most likely find these along ridgelines and in open bowls or mid-slope gullies.  

    Soft slabs will give signs of instability by cracking around your feet or machine.  Hard slabs will support your weight and can break well above you or wider than expected. Avoid both by steering away from obviously wind-affected areas like etched snow surfaces or pillowy dunes. Slabs 8+ inches thick can be troublesome for a rider. Recognize that slab thickness can vary dramatically across a slope. Even small slides can be hazardous if they occur in extreme terrain, above a terrain trap, or trigger a larger avalanche on a buried weak layer. 

     

    (1/16/2025)

    Snow is transported onto a lee aspect, developing new cornice formation and likely forming fresh slabs downwind.

    Photo: Ryan Minton

  • Persistent Slabs

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

    Rocky, wind-affected, alpine slopes facing NW-N-NE-E-SE are where you are most likely to trigger a large avalanche on a buried weak layer. The snowpack on these slopes has variable depth and it is eaiser for a rider to trigger slabs at thin spots, where weak layers are closer to the surface. If you are traveling in this type of terrain, dig below the surface to assess the snowpack structure. Sudden collapses and propagation in tests indicate weak structure. Increase your margin for safety by choosing slopes with planar or concave profiles, deep and consistent snow cover, and minimal overhead hazard. 

    It is possible (but unconfirmed) that large avalanches failed on these layers during last weekend's snowfall and wind-loading. In most cases, layers of surface hoar, facets, and faceted crusts formed in January are buried 3 to 4 feet deep and are unlikely to be affected by a rider.  Larger triggers - like failing cornice or surface slabs - could still trigger large avalanches where weak layers are buried deeply. Persistent Slab avalanche can 

     

    (3/10/2025)

    Although unlikely, there remains a chance a large avalanche failing on buried weak layers could occur. These will mainly be limited to steep, rocky terrain.

    Photo: Michael Reavis

Avalanche Discussion

We’ve got a queue of spring storms eager to push into northwest Montana ahead of next week’s warm-up. I sense that a lot of riders are similarly eager to get out and enjoy the fresh snowfall before it all turns to mush. Don’t let this sense of urgency cause you to take unnecessary risks during a period of elevated danger.

Thursday’s storm favored The Flathead Range, with roughly 8 inches of snow at Tunnel Ridge. The danger is already CONSIDERABLE in this area and will remain elevated during today’s snowfall and wind. Elsewhere, the danger will start at MODERATE. IF today’s snowfall and wind meet or exceed what is forecasted, it is possible we will reach CONSIDERABLE. Pay attention to how much snow is stacking up or blowing around. Fall back to simple, low-angled terrain if you find 8+ inches of new snow or see intense amounts of wind transport.

The biggest and baddest of these storms arrives late tonight and has the potential to drop over a foot of snow (1-inch SWE)—plan on dialing back your terrain choices over the next few days.

I can't believe it. Telefestivus is almost here! Come to Blacktail Ski Area on Saturday, March 22, and Sunday, March 23 to check out the latest and greatest in telemark skiing. Afterwards, Tamarack Brewing will host a fundraiser with a raffle and film for the Friends of the Flathead Avalanche Center from 5 to 8 PM Saturday, March 23. 

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