Avalanche forecast

Northwest 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

On the northern half of the compass, slab avalanches releasing 1 to 3 feet deep on old weak snow have remained a concern all week. This avalanche problem has become more stubborn throughout the week and is showing fewer obvious signs of instability, but by no means has it gone away. On the southern half of the compass, wet avalanche concerns will grow throughout the day. If you find your boots sinking into wet snow, past your ankles or up to your boot tops, it would be good travel advice to just avoid wet avalanche problems and get out of steep terrain or move onto colder slopes. Two natural avalanches released yesterday in easterly terrain. Those avalanches involved both dry snow and wet snow, highlighting the potential to find overlapping avalanche problems in some areas. 

Avalanche problems

  • Loose Wet

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

    Where you find a couple of inches or more of wet snow, human triggering a loose wet avalanche will be possible on steep slopes. These avalanches will start from a point, before fanning out and growing in size as they run through the terrain. Natural loose wet avalanches have mostly run their course on southerly facing slopes, with the concern now focusing on easterly and westerly facing slopes, or anywhere that could power is now becoming wet for its first time. 

    A small wet loose avalanche on Mt Crested Butte earler this week. 

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1.5–2.5

    You can trigger slabs 1 to 3 feet thick that fail on fragile facets below last week's storm snow.  Avalanches can be remotely triggered from below steep slopes and they can propagate surprisingly wide distances.  On slopes that didn't avalanche during the cycle, particularly at lower elevations, the chance of triggering an avalanche hover near 'likely' but given the vast number of slopes that avalanched last week, the reduced distribution of concerning slopes puts the overall likelihood at 'possible'.   To avoid an encounter with a large avalanche, choose slopes that are consistently less than about 30 to 35 degrees that don't connect to steeper terrain above you, or choose slopes with recent evidence of natural avalanche activity.

    This photo from Cement Creek illustrates how persistent slabs can be triggered from a long ways away from the start zone.  The avalanche was remotely triggered by a snowmobile on 2/27.

  • Wet Slabs

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

    The terrain where this avalanche problem could release is fairly isolated and difficult to predict. However, the travel advice is simple. Where you find a wet mess of a snowpack, it is time to avoid traveling on or below steep slopes. An easy gauge for this is if your boots are sinking past your ankles or near your boot tops into wet snow. Meltwater is draining through the snowpack, and when it reaches dry weak layers for the first time, large wet slab avalanches can release. That water drains through individual slopes at different rates. In some areas, the water has already drained and erased the concern, while in others the water may just be about to reach those dry weak layers. The most concerning areas from this problem are upper elevation southerly facing slopes, and where the previously dry snowpack on east and west-facing slopes is now becoming wet. 

    A natural Wet Slab avalanche from Monday 2/28.  Meltwater from warm temperatures and solar radiation infiltrated the facets from February and caused the failure of this dangerous slab.

Avalanche Discussion

The news this week is the hot weather. Penguins would be absolutely melting out there. High temperatures have reached their highest levels of the year, pushing into the upper 40's to low 50's at 11,000ft and even into the 40's at 12,000ft. While overnight low temperatures have only just dipped below freezing in some locations, or into the teens and twenties in other locations. Dramatic changes in the weather lead to dramatic changes in the snowpack. In the avalanche forecast, we've seen the addition of the wet slab avalanche problem and the growing focus on the wet avalanche problems as a whole. As the temperatures have continued to climb, we've seen those wet avalanche concerns spread from southerly facing slopes to easterly and westerly facing slopes. 

Wet avalanche concerns today, are similar to yesterday. The wet slab and loose wet avalanche concerns were split into two separate problems. We are always just searching for the right balance in the level of simplicity to describe conditions. There is some more data helping to describe the locations for the specific problems, but otherwise, their isn't a dramatic change from yesterday. 

The next storm is incoming and we'll see rising avalanche danger by the weekend. Once we see cold weather, the southern half of the compass will get locked up for wet avalanche concerns, and depending on how the snow surfaces shape up we will probably not have to worry about persistent slab avalanche concerns for those aspects during the next storm. 

Regions covered