Avalanche forecast

Southeast Mountains

Crested Butte Avalanche Center
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Avalanche danger

Fri
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
2 · Moderate
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Highlights

Persistent slab avalanches releasing on layers of old snow remain the primary avalanche problem in the SE Mountains. The most likely areas for triggering this avalanche problem will be trigger points, and where the total snowpack depth is relatively shallow between about 80cm and 140cm in depth. A new round of wind slabs will begin forming today as winds are forecasted to increase out of the east. Keep an eye out for these wind slabs forming in unusual or atypical locations. 

Avalanche problems

  • Persistent Slabs

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

    In the Southeast Mountains, slabs breaking on older weak layers are becoming more difficult to trigger but remain a concern on many slopes.  The most prominent and active weak layers are surface hoar and facets buried a couple feet deep on the north half of the compass. There is also smaller 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 deeper and wider than you might expect.  Avalanches breaking into old weak layers are unlikely on mid to low elevation, southerly aspects.  Slope angles consistently less than 30 degrees are a reliable way to avoid the problem.

    This large avalanche was remotely triggered in West Brush Creek on March 8th. 

  • Wind Slabs

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

    Last Tuesday, westerly winds were strong enough to produce wind slab avalanche activity on lee terrain features. We have since seen the wind direction vary from the southwest, on around to the west, and eventually north last night. Winds are now forecasted to increase today out of the east. This changing wind direction has formed wind slabs around much of the compass. Low-density snow that accumulated earlier this week may make small wind slabs surprisingly reactive in some locations today. Look for cracking underfoot or blowing snow to identify signs of instability. Wind slabs will be most common below corniced ridgelines or in cross-loaded terrain featuers. Those fresh drifts will be the most dangerous above terrain traps like cliffs, trees, or gullies. 

    A couple of small wind slabs that ran naturally on Gothic Mtn last Tuesday. 3/12.   

Avalanche Discussion

A layer of very low-density snow accumulated earlier this week. Below 11,000ft on southerly facing slopes, this snow has been cooked away. While on some northerly facing slopes, it was preserved under the recent new snow. We don't currently expect to have enough new snow to create much of a widespread storm slab avalanche problem, but we may see some soft slab avalanche activity become surprisingly reactive if this layer of snow is preserved under fresh slabs. This will most likely occur where the wind has added some additional wind-loading. Yesterday an observer reported fast-running sluffs in steep terrain, and we can expect more of the same today, in more wind-sheltered areas. 

Snowfall over the past few days is gradually adding small amounts of stress to our persistent slab problem.  The pattern of triggered and natural persistent slab avalanches over the past 2 weeks clearly points to areas with shallower snowpacks being the most problematic.  Most of the avalanche activity has been in the shallower part of our forecast area (the Southeast Mountains), and the few persistent slabs in the deeper zone occurred on windward slopes or on slopes that have repeatedly avalanched this season keeping the snow depth unusually shallow.  It's an appropriate time to step out if you are choosing slopes with consistently deep snowpacks (>200cm), or choosing southerly aspects with strong crusts near the snow surface.  This video of a recent persistent slab on Gothic shows how shallow spots and variable snow depths are more common in wind-affected, alpine terrain.   

CBAC Event:  Don't forget the 50th Al Johnson Race is this Sunday, March 17th.  Registration and information can be found at cbavalanchecenter.org.  All proceeds to benefit the CBAC.

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