Avalanche forecast

Swan Range

Flathead Avalanche Center
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Avalanche danger

Sun
Alpine
3 · Considerable
Treeline
2 · Moderate
Below
1 · Low
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Highlights

Recent wind and snow have stressed weak layers buried deep in the snowpack. Decrease your risk by limiting travel on and below steep, wind-drifted slopes. Avalanches can break well above you, wider than expected, and will be difficult to escape.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–2.5

    Today, winds could shift to easterly and transport new and recent snow onto atypical slopes. This could result in thin and sensitive drifts on slopes that are usually sheltered or windward.  These slabs should remain small and relatively harmless. Consider moving to lower-angle terrain if today's snowfall overproduces and you find 8 or more inches of new or wind-drifted snow.

    During the previous 5 days, moderate to strong southwesterly winds drifted snow onto leeward slopes along ridgelines and cross-loaded gullies.  Winds peaked Thursday afternoon and have been tapering off since. Slabs range from soft to hard. Soft slabs may crack around your feet or machine to warn you of their instability.  Hard slabs will not do this until it's too late.

    For the best and safest riding, seek out sheltered slopes. Scalloped snow surfaces and dune-shaped drifts are visual indicators of wind-affected snow. However, today's snowfall may cover these features and make it more difficult to identify wind slabs. If your skis, board, or machine start to ride on top of a stiff, hollow-sounding surface, you've likely found a wind slab.

    Remember that even a small slide can step down to a deeper weak layer, resulting in a larger, more destructive avalanche, as described in the Persistent Slab problem below.

    (2/28/2024)

    Shooting cracks, like these, are a clear sign that recent winds have formed unstable slabs and a good reason to seek out low angle terrain.

    Photo credit: David Kerner.

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    2–3

    Slides can break 2-4 feet deep on a layer of weak, faceted snow in steep, shaded terrain at upper and middle elevations. This layer is found several inches above a stout crust formed in early February. It has been difficult to identify in snowpits and does not always produce concerning results in stability tests.

    This week, snow and strong winds overloaded buried weak layers, resulting in large destructive avalanches, most notably in the Flathead Range and southern Glacier Park. Natural avalanches ran on this layer Thursday in John F. Stevens Canyon. Human-triggered avalanches during the President's  Day weekend resulted in several accidents and near-misses in the Marion Lake area. The structure has been reported across the region and was the cause of a fatality in the Canadian reaches of the North Fork of the Flathead River on Feb. 24.

     Slabs can break well above you, wrap around terrain features, and will be difficult, if not impossible, to escape. They can also be triggered remotely or sympathetically from below or adjacent slopes. 

    (2/29/2024) Crown of large hard slab avalanche that failed on the night of February 28 on the north face of Devil's Hump. Photo: Adam Clark

Avalanche Discussion

The snow surface took a beating this week from moderate to strong southwesterly winds. Yesterday (Friday), Blase and Sarah were East of WMR, where they noted improved weather and stability but generally worse riding conditions than the previous day’s. Although the winds have relented, and natural avalanche activity is unlikely today, it is still possible for a rider to trigger a deadly avalanche, particularly on upper-elevation leeward slopes.  

North of the advisory area, a Special Public Avalanche Warning is in effect for most of British Columbia’s and Alberta’s forecast regions. This warning concerns recent loading on “prominent weak layers established during drought conditions in February.” That should sound familiar since a similar structure has been found across our region.

We received less snow than our neighbors to the north, but we had plenty of wind to make up for it. Thursday, BNSF Avalanche Safety reported a handful of large to very large natural avalanches in John F Stevens Canyon. These slides likely ran sometime late on Wednesday, occurred on wind-loaded slopes, and several may have failed on buried weak layers. Friday, we received similar reports of several very large avalanches in the Middle Fork drainages. These recent slides indicate that the persistent weak layer has not fully healed and still demands caution.

Regions covered