Avalanche forecast

Southeast Mountains

Crested Butte Avalanche Center
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Avalanche danger

Sun
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
2 · Moderate
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Highlights

A quick-hitting storm will deposit 4 - 8 inches accompanied by drifting snow from westerly winds.  Expect small surface slabs to develop throughout the day on leeward features as winds transport snow. Of greater importance is the potential for you to trigger a dangerous avalanche that fails deeply if you find a shallow spot on a slope where slabs are thin.  Slopes that previously avalanched and subsequently refilled remain suspect for triggering a dangerous avalanche.  You can reduce your chance of triggering an avalanche by choosing wind-sheltered terrain and favoring south-facing slopes over northerly-facing terrain.  

Avalanche problems

  • Persistent Slabs

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

    The snowpack structure for this avalanche problem is the most widespread on the northern half of the compass, where buried layers are the most fragile. Slabs have grown stubborn to human triggers because of how thick they are. You are most likely to trigger a monster avalanche where slabs are thinner. Thin areas are more common at higher elevations where the wind has redistributed snow into variable snow depths, and where the snowpack thins near rock outcrops. These widely propagating and long-running avalanches would break 3 to 5 feet thick or more on weak layers near the bottom of the snowpack.  

    A persistent slab avalanche on an east aspect of Hunter Hill. This avalanche released at the start of the new year. 

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–1.5

    Moderate to strong westerly winds will drift the new storm snow into shallow slabs on leeward aspects and cross-load windward features.  Reports of small Surface Hoar formation on some shaded near treeline terrain may make Wind Slabs a bit more reactive.  Wind Slabs will be most commonly found beneath ridgetops, underneath corniced features, and cross-loaded in windward gullies.  Active snow transport will provide clues on distribution if visibility allows.  Cracking on small, drifted features is good evidence of a sensitive Wind Slab problem.

    A Wind Slab avalanche was observed last week below an alpine ridgeline.  You can expect similar slab formation today at upper elevations.

Avalanche Discussion

Your primary focus for managing avalanche risk today should revolve around the lower likelihood yet high consequence Deep Persistent/Persistent Slab problem.  Take a look at this video Zach Guy produced recently for some good points on how to manage the problem.  Slopes that face the north half of the compass offer a significant increase in hazard as compared to south-facing terrain.  Alpine terrain has experienced dramatic wind effects and redistribution over the past week, leaving slabs of variable thickness across the landscape.  The wind redistribution leaves shallow spots and areas with thinned slabs where the weight of a person could impact deep weak layers and release a dangerous avalanche.  Additionally, terrain that avalanched in early December or during the first part of the Santa Slammer storm has thinner slabs that are more prone to human-triggering.  Take a look at this observation from Climax Chutes indicating "unnerving structure" on terrain that avalanched on 12/10 and 12/24 with weak layers remaining intact high in the start zone.  You can also take a look at this observation from Snodgrass on 12/10 with a profile of a bed surface that clearly indicated weak layers remained intact after the natural avalanche.  There is uncertainty about the sensitivity of human-triggering on previously avalanched and subsequently refilled features, but it's worth a skeptical eye and conservative mindset until proven otherwise.  You can utilize the Observations Page and Avalanche Table to help determine what terrain has already avalanched this season.

With a fresh round of snowfall today and strong westerly winds above the treeline, another round of Wind Slab formation may occur.  Snow totals look to max out at 8 inches in the Northwest Mountains with lesser amounts in areas near town and to the east, so Wind Slab formation is expected to remain on the smaller side particularly for the Southeast Mountains.  Use caution on terrain features where you clearly identify drifted snow and if you experience cracking on small test features. 

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