Bulletin d’avalanche

Lionhead Area

Gallatin NF Avalanche Center
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Danger d’avalanche

Alpin
4 · Fort
Limite forestière
4 · Fort
Sous la limite
3 · Marqué
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Périmé — ce bulletin a expiré 8 months ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

Very dangerous avalanche conditions exist in the Lionhead area near West Yellowstone. Avoid all avalanche terrain today which includes runout zones. Don’t get underneath steep slopes. Only ride slopes less than 30 degrees in steepness that aren’t steep enough to slide with nothing steeper above.

Problèmes avalancheux

  • Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Very Likely
    Taille
    2–3

    Many slopes avalanched between Christmas and New Years. They are now reloaded with snow and will easly slide again.

  • Storm Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely
    Taille
    1–2

    Even if avalanches don't break on weak layers near the ground, there's a good change they'll break within all the new snow

Avalanche Discussion

The pattern of danger and avalanche problems across the forecast area is very complex today - bear with me. The simplest solution as always is to avoid avalanche terrain and  enjoy slopes less than 30 degrees in steepness with nothing steeper above you. 

The Lionhead area near West Yellowstone has a HIGH danger and an Avalanche Warning. I’m not sure if natural avalanches will be happening on their own, but I bet you can easily trigger avalanches. Avoid all avalanche terrain and stay far away from avalanche runout zones. 

  • This area has received over 3 feet of snow (4.5” of water) over the last 5 days
  • A widespread avalanche cycle occurred during the last week of December thru New Years that Ian observed on Jan 2 with many avalanches breaking on facets  near the ground
  • Dave and I returned on Jan 5 and discovered that all the slopes that had previously avalanched were ready to slide again (repeaters) when we triggered one of them.
  • With up to 4.5” of water weight in the new snow combined with strong winds transporting snow the last two days, weak, faceted snow near the ground is at its tipping point.

All other areas have a CONSIDERABLE danger mostly the result of strong winds the last two days that have been transporting lots of snow. Ski patrols, guides near Cooke City, and backcountry skiers in the Bridgers and Hyalite have all triggered fresh wind slabs. Wind slabs may vary in size based on snowfall in the different areas. The good news about this problem is that you can use visual clues to identify locations to avoid. 

There are other avalanche problems in certain zones complicating the situation.

Persistent slab avalanches breaking on facets near the ground are still a major issue in the southern Madison and Gallatin Ranges. These avalanches may break 3-5 feet deep. Because the weak layer is buried so deeply, you may not see obvious clues like collapsing, whumpfs, or shooting cracks. The red flags are (1) knowing a layer of facts is lurking under your feet, and (2) the combination of heavy snowfall and strong winds. This same problem exists in the northern Madison and Gallatin ranges, but these areas have gotten minimal snow, thus this problem is unlikely.

Storm slab avalanches should be considered in the Lionhead and Island Park areas where over 3 feet of snow has fallen in the last 5 days. This problem will be tricky because it may feel safer down in the trees out of the wind zone, but with so much new snow, storm slabs or even a sluff could be big enough to bury you.

We were saddened to hear of a rider killed in a wind slab avalanche 3 days ago near Lake Tahoe in California. The avalanche was 1-2 feet deep and 330 feet wide.

Régions couvertes