Avalanche forecast

Swan Range

Flathead Avalanche Center
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Avalanche danger

Fri
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
2 · Moderate
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Out of date — this forecast expired 5 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

Dangerous avalanche conditions exist at mid and upper elevations. You’ll likely trigger large slabs of new and drifted snow or fast-moving sluffs if you venture onto steep slopes. Choose terrain with slope angles less than about 35 degrees. Red flags like shooting cracks and recent avalanches should only confirm your conservative mindset.

Avalanche problems

  • Storm Slabs

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

    New and drifted snow have formed dangerous slabs on slopes steeper than about 35 degrees. These can entrain a lot of loose snow and be large enough to bury you. You can test the new snow to see if it's a cohesive slab with test slopes and hand pits. Shooting cracks and recent natural avalanches are warning signs telling you to stick to simple terrain with low slope angles.

    (3/23/2021) Natural storm slab avalanches on Nyack Mountain.

  • Loose Dry

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

    Dry sluffs can entrain a lot of debris on very steep, sheltered slopes. You can manage the risk of getting carried or buried by fast-moving loose snow by avoiding confined chutes and the slopes underneath them. Choose simple terrain with lots of options and slope angles less than about 35 degrees to avoid the problem.

    (3/24/2021) Skier triggered loose dry avalanches on steep slopes.

  • Persistent Slabs

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

    Although it is unlikely, it is not impossible to trigger a very large hard slab avalanche failing 2 to 6 feet deep on shaded aspects above 6500 feet. Stick to slopes less than 35 degrees if you do not feel a supportable crust in hand pits under the new and recent snow. Avoid slopes near rocky outcrops, with variable snow cover, or with cornices overhead. Cornice fall or a smaller avalanche can be the trigger that sets off a destructive slide. The last reported avalanche failing on mid-winter weak layers was over a week ago. Though the potential consequences of being caught by surprise should keep the hazard in the back of your mind.

    (3/17/2021) The crown from a hard slab avalanche that's more than a few days old.

Avalanche Discussion

Snowfall over the past 24 hours has created dangerous avalanche conditions where the most snow fell. In other areas, you'll have to assess the hazards carefully before stepping into committing terrain.

As snowfall increased Wednesday afternoon, Cam found loose dry avalanches becoming larger and easier to trigger in the southern Whitefish Range.

Since mid-day Wednesday, Noisy Basin has picked up 10 inches of snow and 1.4 inches snow water equivalent (SWE). Big Mountain came in second with 7 inches and almost an inch of SWE. Much less fell to the east. The Flattop SNOTEL reports just 3 inches of snow and 0.3 inches of new water. Aside from some residual showers, the bulk of the precipitation has moved south and east. Winds were at perfect snow-blowing speeds at Hornet Lookout, Mt. Aeneas, and the Snowslip weather station for most of the storm. Though they have decreased and shifted to the north.

Wednesday’s new snow fell on 4 to 12 inches of loose, low-density snow near and above treeline on shady aspects. Underneath that, recent snow rests on old rain and melt-freeze crusts to about 6,500 feet, old wind slabs near and above treeline, or near surface facets.

Deeper in the snowpack, mid-winter weak layers sit 2 to 6 feet deep. These layers have been unreactive for more than a week.

Glide cracks litter steep east to south to southwest-facing slopes above about 5,500 feet. New snow may make them difficult to see. It’s best to avoid slopes near and below them.

Regions covered