Avalanche forecast

Southeast 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

Yesterday's large natural avalanche off of Mt. Crested Butte (see video) demonstrates our ongoing concerns for triggering a persistent slab that fails several feet deep.  The safest riding is in wind-protected terrain in areas with a snowpack consistently deeper than about 6 ft or on southerly facing terrain.  Choose simpler terrain on the north half of the compass in areas where the snowpack is around 3 to 5 feet deep, especially in variable or rocky areas.

Avalanche problems

  • Persistent Slabs

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

    In the Southeast Mountains, high-consequence slabs breaking on older weak layers are becoming more difficult to trigger but remain a concern on the north half of the compass, or potentially on a few southerly slopes above treeline.  The most prominent weak layers are surface hoar buried a couple of feet deep and depth hoar near the ground.   Persistent slab avalanches can be remotely triggered from low-angle terrain and break deeper and wider than you might expect.   Triggering avalanches are unlikely on mid to low-elevation, southerly aspects, or areas where the snowpack is consistently deeper than 200 cm.  Slope angles consistently less than 30 degrees are a reliable way to avoid the problem.

    A large persistent slab on Mt. Crested Butte that ran on 3/16.  This slope is shallow, variable in depth, and on the north half of the compass: a combination of ingredients you want to avoid.  

Avalanche Discussion

Wind transport has largely ended after easterly winds peaked on Thursday and Friday.  Most of the shallow wind slabs that formed earlier this week (ex. 1, ex 2) have healed up by now.  Isolated exceptions may exist on very steep or heavily drifted features.

The big news comes from the dramatic display of our persistent slab problem out of the Terminator Chutes yesterday evening.  The slab broke on basal weak layers on a seasonally shallow northwest-facing slope that likely saw some wind loading earlier this week from abnormal winds.  It looks like it might have been triggered naturally by a period of solar warming, or maybe it was Zane saying hello 9 years later.  Regardless, the shallow and variable snowpack in Terminator 3 has all the ingredients to stay away from today. This recent large avalanche near Copper Creek further illustrates the problem.   Our fieldwork yesterday demonstrates how slopes with a deeper snowpack are relatively stronger and more trustworthy.  This is why the deeper snowpack of the Northwest Mountains is at Low danger today.  You can significantly reduce the risk of triggering a large avalanche by traveling where the snowpack is consistently deeper than about 200 cm (~6 feet), or by traveling on slopes with thick, supportive crusts near the snow surface (most commonly on the southern half of the compass). 

CBAC Event:  The 50th Al Johnson Race is today! It's not too late to sign up. Last-minute registration and mandatory bib pickup are 9 a.m. to 11  a.m. at the Treasury Center.   Race starts at 1 p.m. at the bottom of the North Face Lift.  Party and awards at Butte 66 at 3:30.  All proceeds to benefit the CBAC.

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