Avalanche forecast

Northwest Mountains

Crested Butte Avalanche Center
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Avalanche danger

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

The safest riding is in wind-protected terrain.  At higher elevations, stay alert for shallow but stiff drifts from unusual east winds.  They generally aren't large enough to bury you, but they could break above you and carry you into trees, rocks, or gullies.  There is rare potential to trigger a much larger avalanche that fails on old weak layers where the total snowpack height is below average and variable in depth, like this avalanche on Mt Baldy.

Avalanche problems

  • Wind Slabs

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

    The past two days of east and southeast winds have drifted this week's snow into denser and thicker deposits on the leeward sides of gullies and ridges.  Read the surface textures to identify problematic features:  wind slabs will look smooth and rounded.  Consider terrain consequences and potential slab size before riding across steep, windloaded terrain.  

    A small wind slab on the lee side of a cross-loaded terrain feater. Mt Axtell, 3/14.

  • Persistent Slabs

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

    In the Northwest Mountains, high-consequence slabs breaking on older weak layers have become isolated and difficult to trigger. Persistent slabs are most likely triggered from a shallow, previously wind-eroded slope where the total snowpack height is below average, or from random cornice falls. Persistent slab avalanches can be remotely triggered from low-angle terrain and break deeper and wider than you might expect.  The most problematic structures are on shallower slopes on the north half of the compass.  Mid to low-elevation, southerly aspects have the most trustworthy snowpack.  Slope angles consistently less than 30 degrees are a reliable way to avoid the problem when in doubt.  

    The crown of a very large persistent slab remotely triggered by snowmobiles on March 8.  This slope is west facing and eroded by seasonal winds, making for a shallower and more problematic snowpack than other slopes. 

Avalanche Discussion

This week's major upslope storm made the news headlines for 3 to 4 feet of snow in the Front Range, but here in the rainshadow, we saw only modest snowfall (~5" to 10") and pesky easterly winds.  The wind slabs that formed during the past few days are neither large nor widespread, but enough to warrant caution in consequential terrain. Here are a few examples of the problem from Mt. Axtell and near Marble.  And because winds were blowing opposite their normal direction, expect to find drifts in unusual features.  Softer, wind-sheltered snow will provide safer and higher-quality riding today as we give wind slabs another day to heal up before they're likely pulled off the list tomorrow. 

Persistent slab activity has quieted down since March 9th.  Some of this may be attributed to fewer human triggers during a work week featuring grey weather.  However, a lack of significant loading and a cooler weather pattern this week are causing buried weak layers to become increasingly stubborn following a flurry of avalanche activity during last week's big storm and subsequent warmup.  Although the likelihood of triggering a persistent slab has declined, the consequences and our messaging, remain the same:  slopes with shallow and variable snow depths are most concerning.  That's where our buried surface hoar and early-season facet layers are both weaker and easier to impact. More slopes in the Southeast Mountains fit this description, though potential troublemakers exist in both forecast zones.  You can significantly reduce the risk of triggering a large avalanche by traveling where the snowpack is consistently deeper than about 200 cm (6 feet), or by traveling on slopes with thick, supportive crusts near the snow surface (most commonly on the southern half of the compass).

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