Avalanche forecast

Flathead Range & Glacier NP

Flathead Avalanche Center
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Avalanche danger

Fri
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
2 · Moderate
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Highlights

Dangerous avalanche conditions exist. Riders triggered avalanches large enough to bury a person from a distance the last two consecutive days. Steep north and east-facing slopes have the potential for very serious consequences. Stick to slopes less than 30 degrees. Warm temperatures and the sun may weaken the snow surface and cause a round of natural wet loose avalanches. Plan your day to avoid being on or under steep south and west-facing aspects during the PM hours.

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1.5–2.5

    Shaded slopes at roughly 6000 to 6500 feet are the hot spots for human-triggered avalanches. The weak layer responsible for this extends well above 6500 feet and down to around 5000 feet. Don’t allow blue sky and powder snow blind you from the dangers lurking below the surface. Slabs can break 1 to 3 feet thick, propagate wide distances, and be triggered remotely. Triggering remotely means you can walk on low angled terrain and trigger a slide that comes down on top of you. Managing slope angle is your key. Travel on and below slopes less than 30 degrees.

  • Loose Wet

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–2

    Warm temperatures and solar radiation will likely cause a round of natural wet loose avalanches. I expect these slides will entrain enough debris to be large enough to bury a person. You will feel the most heat during the PM hours, just in time for your descent or exit. Plan both of those to avoid south and west-facing slopes. Rollerballs and point releases out of the rocks are your first signs this problem is beginning to happen.

    (3/6/2022)

    A couple of small point releases turned into a Wet Loose avalanche as they entrained snow moving downhill.  

    Photo: Mark Dundas

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1.5–2.5

    Winds continue to blow at transportable speeds, drifting snow onto leeward aspects below ridgelines and cross-loading gullies further down. Look for pillowy surfaces and blowing snow for key areas to avoid. There is a possibility that a triggered wind slab may step down to a much larger, persistent slab avalanche.

    (2/25/2022) Evidence of wind drifted snow. Look for surface clues to identify where slabs of drifted snow exist.

    : Mark Dundas

Avalanche Discussion

A weak layer of buried near-surface facets is responsible for the recent remotely-triggered avalanches and natural avalanches the past two days. This avalanche problem is dangerous and one to not take lightly. If you venture onto north and east facing slopes, manage your slope angle. Utilize ridges for safer travel and don’t venture onto anything steeper than 30 degrees. Seek out powder snow on low-angle terrain.

Note: We broadened the distribution of persistent slab to include west aspects on Tuesday because of uncertainty about the distribution of buried weak layers. So far there is no evidence this problem exists on south aspects. A sun crust located above the weak layer is reducing the chances for triggering on those aspects. This is subject to change when and if we receive a loading event from snow or rain.

I wish I had an aspect I could point to and say “have at it.” Unfortunately, that is not the case and warm sunny weather is adding complexity to today's travel conditions. This is why we are keeping the danger elevated and raising at mid-elevations in the Whitefish Range. There may be a short window to ride on steeper slopes on southerly aspects this morning. However, I strongly suggest avoiding south and west aspects once you begin to feel the warm sun on your back. Be sure to plan your afternoon exit to avoid solar aspects given that will be the warmest part of the day.

Winds have thickened slabs on leeward terrain features. Slabs of drifted snow are gaining strength, but they rest on the same side of the compass that weak layers are buried on. Feedback will become sparse in zones where the weak layer is buried further down. At this stage in the game, it is not buried far enough to make it less likely to trigger. 

Travel cautiously and be patient.

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