Avalanche forecast

Northwest Mountains

Crested Butte Avalanche Center
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Avalanche danger

Mon
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
2 · Moderate
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Highlights

This will be a great day to ski and ride in the NW Mountains forecast area while primarily managing new snow avalanche problems. Overnight south to southwest winds have formed wind slabs on the lee sides of ridgelines and cross-loaded terrain features. In wind-sheltered areas, you can expect to encounter more of a loose snow avalanche problem. Take time to investigate these avalanche problems today, and make a plan to manage them in the terrain you want to ride. There is a very low possibility of triggering an avalanche that breaks deeply into the snowpack. The most suspect areas for those persistent slabs would be an area with a variable snowpack depth such as extreme rocky terrain or northwesterly wind-exposed terrain. 

Avalanche problems

  • Wind Slabs

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

    Last night, the Cinnamon Mtn weather station at 12,000ft recorded southerly winds in the 20 to 30mph range with gusts in the 40's and 50's. While other weather stations recorded notably lighter wind speeds. Forecasted winds eventually become light and back to the west and northwest today. Fresh wind slabs have formed on the lee sides of ridgelines and cross-loaded terrain features. Plan to either avoid wind-loaded terrain today or investigate how reactive and large those slabs are before committing to wind-loaded terrain. 

    Example of a wind slab that formed in a cross-loaded gully.

  • Persistent Slabs

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

    In the Northwest Mountains, high-consequence slabs breaking on older weak layers have become isolated and difficult to trigger. The last observed persistent slab avalanche occurred on March 8th in this forecast area. Any lingering persistent slabs would most likely be triggered from an unusually shallow or previously wind-eroded slope where the total snowpack height is below average.  Large cornice falls could act as triggers as well. Persistent slab avalanches can be remotely triggered from low-angle terrain and break deeper and wider than you might expect.  Slope angles consistently less than 30 degrees are a reliable way to avoid the problem when in doubt.  

    The crown of a very large persistent slab remotely triggered by snowmobiles on March 8.  This slope is west facing and eroded by seasonal winds, making for a shallower and more problematic snowpack than other slopes. 

Avalanche Discussion

Here are the 5am Snow Totals:

NW Mountains: Schofield Pass 7" snow and .6 to .9 SWE. Elkton ~5" snow. Irwin ~4" snow and .4 SWE.  

SE Mountains: Brush Creek 11,000ft 5" snow. CBMR 3.5" snow and .3 to .4 SWE. Upper Taylor 5" snow and .5 SWE.

The most likely to encounter avalanche problems today will be fresh wind slabs. Given the current amount of snow and decreasing wind speeds today, most of those wind slabs will be small in size. The Ruby Range and areas with a big fetch of snow avalible for transport, could be holding large wind slabs. These slabs have formed over crusts and some small facets on northerly-facing slopes. Forecasted winds pick back up into the 20's from the NW to N, later this afternoon and overnight with more snow in the forecast. 

The last persistent slab avalanches were observed on March 8th in the Northwest Mountains, and more recently on March 16th in the SE Mountains. Concerns for additional persistent slab avalanches have mostly been for areas with a relatively shallow snowpack where persistent weak layers have remained more pronounced. The persistent slab problem rose was trimmed to cut out areas that have seen recent meltwater draining into the snowpack, and now those old snow surfaces have started to refreeze. Both forecast areas made it through the last week of warm weather without any slab avalanche activity. It would have been nice to see some cornices fall and test some slopes, but we weren't so lucky. The problem rose now covers northerly facing slopes at near and above treeline elevations. Many below treeline slopes formed crusts or saw water running deep into the snowpack. Isolated exceptions would include a few due north to northwest facing slopes at lower elevations. The most suspect slopes are likely northwest-facing above 11,000ft, as those areas will more commonly have a shallower total snowpack height and more pronounced weak layers.

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