Avalanche forecast

Swan Range

Flathead Avalanche Center
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Avalanche danger

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

Dangerous avalanche conditions exist and an avalanche watch is in effect for the Swan and Whitefish Ranges. Warm temperatures and solar radiation will weaken the snowpack throughout the day and cause avalanches large enough to bury, injure and kill a person. Stick to conservative terrain and expect increasing avalanche danger as the day progresses. 

Avalanche problems

  • Loose Wet

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

    Sun-baked terrain will produce wet avalanches large enough to bury, injure, or kill a person. Today’s sunny weather and warm temperatures will wet the surface snow, causing destructive avalanches. Rollerballs or pinwheels are signs that conditions are ripe for wet loose avalanches. To reduce your risk of this problem, seek out shaded, northerly-facing slopes. Plan your day to avoid crossing below south and west-facing avalanche paths, especially later in the day.  

    (3/3/2021) New, Large Avalanche Apgar Range

  • Persistent Slabs

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

    Recent avalanches and loud collapses are signs to stay off and out from underneath terrain steeper than 30 degrees. Yesterday we observed five natural slab avalanches failing on southwest aspects in the Whitefish Range. I’d expect this kind of activity to continue today with warming temperatures. Other likely triggers will be falling cornices, and you. The only way to manage this problem is by avoiding avalanche terrain.

    (3/3/2021) Slab Avalanche Triggered By Solar Input, Whitefish Range

  • Glide Cracks

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

    What looks like brown frowns on solar aspects are glide cracks. The entire snowpack is slumping and slowly sliding down the hill on smooth ground underneath - like bear grass or bedrock. They can fail all at once resulting in very large and dangerous avalanches. That’s more likely to happen when sun and warming temperatures lubricate the bed surface with fresh meltwater. Avoid traveling on slopes beneath these large cracks in the snow.

    (3/1/2021) The brown frown. Glide crack opened up 2/28 or 3/1

Avalanche Discussion

Today there are honestly more problems than we can put on the list. Yes, there are loose wet avalanches, persistent slab avalanches, and the possibility of glide avalanches. We discussed falling cornices and even wet slabs as runner-ups this morning. Today is a good day to stick to ridgelines and soak up the sun in a t-shirt. Avoid avalanche terrain altogether.

Yesterday we saw the first real round of wet loose activity (Apgar Range, Northern Whitefish Range). Most of these naturals were observed mid-afternoon on southwest aspects. I’d expect to see more widespread activity today with warmer temperatures, calmer winds, and less of a refreeze overnight. Avalanches will be larger and more destructive in the Flathead Range and Glacier National Park where there is more vertical relief for avalanches to pick up more speed and entrain more snow. Remote weather stations also showed no refreeze, or a brief period of temperatures below freezing in the Flathead and Glacier National Park. Areas that did not see a refreeze will be more dangerous today. Areas where you find a melt-freeze crust this morning will be become unstable later in the day once that crust breaks down.

Loud whumpfing collapses and solar-triggered avalanches yesterday makes me nervous about what is to come. It seems inevitable that we will see more of this activity today and tomorrow. Unfortunately, there is no aspect that holds safe snow. Large cornices hang over north and east-facing slopes where the bulk of the avalanche activity has been, and south-facing slopes avalanche yesterday due to warm temperatures and solar radiation. Keep it simple!

Regions covered