Avalanche forecast

Southeast Mountains

Crested Butte Avalanche Center
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Avalanche danger

Thu
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
2 · Moderate
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Highlights

Although conditions are gradually improving under the quieter weather pattern of the past week, the Southeast Mountains have been the problem child in recent weeks for triggering dangerous avalanches that break several feet thick or more.  Recent human-triggered avalanches and continued signs of instability highlight our concerns.   Choose less consequential terrain and lower slope angles on the north half of the compass to manage the problem.  You can find safer riding on southerly aspects where you find a few inches of new snow over thick crusts. 

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1

    3" to 8" of snow has accumulated in the past two days and westerly winds have been strong enough to drift the snow into shallow slabs at higher elevations.  Look for cracking underfoot or blowing snow to identify signs of instability.  Wind slabs will be most common below corniced ridgelines or in crossloaded gullies above treeline.  Fresh drifts will be most dangerous above terrain traps like cliffs, trees, or gullies. Seek out wind-protected terrain to avoid the problem.  

    A couple of small wind slabs that ran naturally yesterday on Gothic Mtn.  

  • 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 8.  

Avalanche Discussion

The danger continues to slowly creep up today with another 2" to 5" of snow overnight (up to .5" of SWE) and a few more inches of new snow expected today.   Gradual snowfall over the past two days and light to moderate winds aren't creating significant storm instabilities, but there's been enough drifting snow to form some shallow wind slabs at higher elevations, exemplified by this observation on Gothic Mountain yesterday.   Monitor storm totals, wind drifting, and terrain consequences to manage new snow issues today.  

Snowfall over the past two 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.   

Some weather models are calling for significant snow totals tonight accompanied by increasing easterly winds tomorrow.  Winds from the east loading onto our traditionally shallow and windward aspects is a notable change to pay attention to, especially if we see significant snow available for transport.  Stay tuned tomorrow, there's a fair amount of uncertainty about how the storm plays out tonight.  

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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