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

A multi-day warm-up will begin increasing the threat of dangerous wet avalanches.  Early starts and finishes will offer safer travel on the sunny side of the compass.  The snowpack remains problematic on the northern half of the compass with buried weak layers up to several feet deep.  Although feedback and triggered avalanches are becoming less common, the size remains dangerous.  

Avalanche problems

  • Persistent Slabs

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

    Weak facets and collapsible crusts are widespread on the northern half of the compass and on some sunnier aspects at high elevations.  Slabs on top of these weak layers average 2 to 3 feet thick in wind-sheltered terrain. Slabs are thicker and harder in wind-drifted terrain and can step down through older slabs to the ground.    This problem has become stubborn to triggers, often requiring a thin spot on the slope, such as near buried rocks, trees, or where slabs thin from wind effects. Avalanches can break widely across multiple terrain features and be remotely triggered from flat terrain near or below steep slopes without warning signs. The problem can be avoided on slope angles consistently less than about 30 degrees.  

    These destructive persistent slabs released on Wednesday 2/19.  These exemplify the potential size avalanche you could trigger on large, drifted slopes. 

  • Wet Slabs

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

    As meltwater drains into the snowpack, it can weaken the bonds of buried facets or depth hoar layers and cause natural or triggered wet slabs.  Be cautious of steep, sunbaked slopes as temperatures increase later in the day and the upper snowpack gets saturated.  You can avoid the problem by traveling early in the day while the snow surface is still frozen or by moving to cold, shady aspects or low-angle terrain without overhead hazards later in the day.  

    The large slab avalanche in the photo likely failed during warm weather earlier this week due to meltwater draining into the snowpack. 

  • Loose Wet

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

    As the snow surface gets wet and loses cohesion on sunny aspects, you can trigger shallow point release avalanches in the upper snowpack.  These can be dangerous if they push you into trees, rocks, or gain volume in long gullies. There's an isolated chance they can trigger larger slab avalanches.  Look for rollerballs, pinwheels, or ankle-deep wet snow to identify the problem.  You can avoid the problem by moving to slope angles less than 35 degrees or to colder aspects where the snow surface is frozen.  

    A long running wet loose avalanche from earlier this week.  

Avalanche Discussion

North half of the compass:  Due to the current sun angle and clear skies, the snowpack will stay dry or only see minor amounts of meltwater.  On these slopes, the snowpack continues to dawdle along with slow and gradual improvements each day.  Some slopes have already flushed the slab, some have reached equilibrium, and some hang in the balance, capable of producing a large or destructive avalanche.   With infrequent feedback, the latter can be difficult to identify now.  You can reduce your risk by riding on smaller, less consequential terrain with deeper, more uniform snowpacks or by simply managing slope angles.  Stay alert for random cornice falls (ex. OBJ) that could trigger a surprisingly large slab avalanche.  

South half of the compass:  Things start getting interesting, and the danger will increase as the day heats up.  Meltwater started moving through the snowpack last weekend, spurring numerous small wet loose avalanches and a few larger wet slabs.  Today's temperature forecast is similar to what we saw last Saturday - starting quite cold in the teens or single digits and climbing into the 30s- and a modest output of wet avalanches is expected.  As the warmup progresses on Friday and Saturday, wet avalanche activity is expected to become larger and/or more widespread.  Because water moves through the snowpack in unique ways (see videos from Mt. Emmons and Elk Basin), there's always forecaster uncertainty with predicting the onset and spatial extent of wet slab avalanches.  Many low-elevation southerlies have seen water drain through the snowpack earlier this month and lack the poor structure necessary for a wet slab failure.  Poor structures exist on east and west aspects, or at higher elevations on southerly aspects  - those will be the slopes of most concern as meltwater mobilizes over the next few days.  Clear, cool nights will allow the upper snowpack to refreeze and offer a window of safer travel every morning.  Instabilities involving wet snow will develop first on east aspects in the morning, then south, then west later in the day.  Once those crusts thaw into unsupportive wet snow, consider mellower terrain.  

Regions covered