Avalanche forecast

Northwest Mountains

Crested Butte 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Out of date — this forecast expired 2 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

The foot of snow and wind event on Tuesday continues to dictate the avalanche hazard today.  You could encounter dangerous conditions on drifted terrain features; wind-loaded slopes are more commonly found at upper elevations on the east half of the compass, however, extensive down valley winds transported snow in open terrain below treeline.  Avalanches could break in the recently drifted snow but some slopes might break deep into the snowpack.  On wind-sheltered features facing the north half of the compass, you can trigger avalanches several feet deep on layer of surface hoar.  You can find safer travel options on wind-protected southerly slopes, but look for isolated drifts and warming snow surfaces.

Avalanche problems

  • Persistent Slabs

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

    Heavy snowfall and intense wind loading yesterday added significant amounts of stress to weak layers in the snowpack, causing large and dangerous natural avalanches.  Avalanches breaking on old weak layers will be more sensitive to human triggers now that the snowpack is stressed.  The most prominent and active weak layer is buried surface hoar several feet deep on the north half of the compass. There is also potential for avalanches to break on faceted crust layers on some higher, southerly aspects, or depth hoar layers near the ground.  Persistent slab avalanches can be remotely triggered from low-angle terrain and break larger and wider than you might expect.  Low-elevation southerly aspects are significantly less problematic, and slope angles consistently less than 30 degrees are a reliable way to avoid the problem.  

    A broad avalanche on the north side of Crystal Peak that ran during last week's storm.  

  • Wind Slabs

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

    Intense wind drifting on Tuesday formed slabs of varying thickness on wind-loaded terrain features at all elevations.  Tuesday's winds shifted from southwest to northwest, so you will most likely find slabs on the east half of the compass or cross-drifted features elsewhere.   Use visual clues to identify where drifting snow landed: it will look and feel deeper, stiffer, and more rounded.  Some of these slabs will be hard and stubborn already, others are easy to trigger.  You can avoid the problem and find softer, higher-quality snow in wind-sheltered terrain.  Consider slab size and terrain consequences before crossing a drifted slope. Avoid steep slopes where fresh wind loading overlaps with larger persistent slab issues; triggered slabs in the upper snowpack can step down and produce much larger avalanches. 

Avalanche Discussion

Tuesday's snowfall and wild winds produced a natural avalanche cycle on leeward terrain features.  Observers documented around 40 natural avalanches (certainly more out there yet to be observed) with most failing in the recent storm snow but a handful broke into old snow layers.  The most concerning and largest examples come from Axtel (Green Lake, 4th Bowl) which demonstrates the lingering threat for avalanches to break deeply in the snowpack on highly drifted terrain.  At lower elevations, large avalanches ran above Long Lake and Cement Creek.  Outside the CBAC forecast area, multiple very large avalanches ran on Park Cone and in areas near Aspen.

Drifted terrain represents the most concerning location as triggered avalanches are more likely and can grow larger.  The observed avalanche activity suggests most avalanches will break in the recently drifted snow, but a lesser chance remains for slides to break deeply in the snowpack and become deadly.  Some avalanches that only involved recent drifting grew large enough to bury and injure you like this one of Ruby Peak.  It is difficult to predict which slopes will fail deeper as an avalanche triggered in the surface snow could provide enough force to release a deeper slide.  Carefully assess the terrain for signs of recent drifting and avoid places where you see clear evidence of wind loading.  Keep in mind that you may find slopes at low elevations with extensive drifting.

In sheltered areas, the threat of avalanches breaking a few feet deep exists due to our problematic surface hoar layer.  The hazard is most acute in the Southeast Mountains, where slabs remain thin enough to keep the weak layer easily within reach of backcountry travelers.  Examples from Gibson Ridge, Cement Creek, and Long Lake reinforce this point.  Take a cautious and conservative approach to the Persistent Slab problem in the Southeast Mountains.  In the deeper areas of the Northwest Mountains, slabs have grown thicker and stiffer, which helps to insulate the weight of a person from impacting the surface hoar layer.  In these areas, it's still possible for you to trigger a dangerous avalanche from a shallow spot on slope or a step-down avalanche.

Events: The CBAC Fireside Chat Series presents legendary American alpine climber George Lowe on Sunday, March 3 at the Mallardi Cabaret Theatre in downtown Crested Butte at 6 p.m. Best of all, it’s free!

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