Bollettino valanghe

Flathead Range & Glacier NP

Flathead Avalanche Center
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Pericolo valanghe

Thu
Alta quota
2 · Moderato
Limite del bosco
1 · Debole
Sotto il limite
1 · Debole
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Non aggiornato — questo bollettino è scaduto 2 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

Low-angled, planar slopes sheltered from the wind offer the least risky riding today. On shaded, convex slopes above terrain traps, dangerous avalanches that break over 2 feet deep are possible. You can also trigger slides closer to the snow surface on slopes that collect windblown snow. This hazard is more widespread at upper elevations.

Problemi valanghivi

  • Persistent Slabs

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

    It remains possible to trigger avalanches that break 12 to 30 inches deep on weak snow buried in early December. This threat is most widespread on upper-elevation, shaded slopes. It is isolated on mid-elevation and sunny slopes. 

    Recent observations have shown some variability in the sensitivity of this layer. A rider reported whumpfing collapses on a ridge at 6500 feet Tuesday. Cam got propagation in one of two large column tests in the Skyland area Monday. It's hard to hang your Santa hat that variability, however. Any triggered slide will be very difficult to escape and involve more than enough debris to bury or injure a person. That's demonstrated by a large, cornice fall triggered slide that released in the last few days. A classic low-likelihood, high-consequences dilemma. 

    The most straightforward way to manage this lingering hazard is to avoid riding on or below steep, shaded slopes. If you choose to step out, you can reduce the chances and consequences of a nasty surprise by avoiding steep, convex slopes above terrain traps like trees, rocks, and gullies. Slopes with variable snow depths are pockmarked with unidentifiable trigger points. These slopes are often scoured and loaded by cross-slope winds. 

    (12/24/2024)

    Recent natural avalanches on the lee side of the Flathead range show the lingering hazard of triggering large avalanches that break deep in the snowpack 

    Photo: Michael Reavis

  • Wind Slabs

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

    The hazard of triggering slabs of drifted snow exists in the terrain that harbors the persistent slab avalanche problem. It is most widespread near the crest of the Swan and Flathead Ranges, and near summits and ridges in Glacier National Park.  In this terrain, several days of gusty windshave formed slabs of wind-drifted snow. Look for these top-loaded onto lee slopes and chutes, and cross-loaded into gullies. Debris from cornice falls and wind slab avalanches can release slides that break deeper in the snowpack, on the early December persistent weak layer. 

    Cornices overhanging a slope, whale-shaped drifts, and blowing snow are signs of this hazard. Avoid steep slopes with more than about 8 inches of stiff, wind-blown snow.  Play on gladed, low-angled slopes that are sheltered from the wind. This may include slopes that face into the sun today, since last night's snowfall buried any suncrusts.

    (12/20/2024)

    A small wind slab is visible just beneath a cornice near the summit of Elk Mountain. This slide likely failed during the intense wind event of 12/17-18. 

    Photo: Mark Dundas

Avalanche Discussion

Oh, the weather outside’s been frightfulA wintery mix is not delightfulAnd since we need places to go Let it snow, let it snow, let it snow

The slabs show signs of settlingAnd weak grains look less threateningSome brush and stuff down lowLet it snow, let it snow, let it snow

When it finally dumps all nightHow we'll love going out for some turnsBut if we wanna get home all rightWe take an avalanche class and learn

The seas are slowly heatingAnd, darn, winter feels so fleetingBut ARs help the snowpack growLet it snow, let it snow

For the tune, choose a jaunty version by Dean Martin, or a snowpack melter by Doris Day.

Happy Holidays.

Regioni coperte