Avalanche forecast

Northwest Mountains

Crested Butte Avalanche Center
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Avalanche danger

Sun
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
3 · Considerable
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Out of date — this forecast expired 6 months ago. You’re viewing past conditions, not the current bulletin.

Highlights

A Special Avalanche Bulletin remains in effect due to recent heavy snowfall overloading a weak snowpack. The most dangerous conditions exist on west through north through east aspects, as well as wind-loaded terrain on other aspects. Avalanches may run farther than expected, grow to an unsurvivable size, and could be triggered remotely from below or from adjacent terrain.  You can reduce your risk on suspect aspects by choosing low-angle terrain without steep slopes overhead. Low-elevation, wind-protected southerly aspects generally offer a less hazardous snowpack; however, carefully evaluate how well the recent snow is bonding to underlying crusts.

Avalanche problems

  • Wind Slabs

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

    Over the duration of the multi-day storm, winds have typically blown from southwest, west, and northwest directions.  Continued snowfall on Friday provided more fuel for winds to load leeward terrain.  Overnight winds often blew from the west or northwest.  Expect to encounter fresh drifting on easterly and southerly aspects. Most drifting occurred near and above treeline, but maintain a vigilant eye for drifting in open areas at lower elevations.  Due to the incredibly thick slab size on leeward features, the best solution is to avoid wind-drifted terrain regardless of aspect.

    A thick cornice that was remotly triggered on Wedneday in Evan's Basin. 

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    2–3.5

    Persistent slab avalanches will break an average of 2 to 4 feet deep (deeper on drifted terrain) on buried persistent weak layers, and may run naturally today during periods of active loading. These slabs have settled and are not often showing obvious warning signs before large and destructive avalanches release. The north half of the compass has the most fragile weak layers buried in the upper and lower snowpack (see videos 1 & 2) and is most likely to produce natural releases, remote triggers from flat terrain, widely propagating, and destructive avalanches.  Southerly aspects have a more springlike snowpack structure, reducing the likelihood that avalanches break deeper and larger than the storm snow.  Manage today's persistent slab problem by avoiding travel on or below terrain steeper than 30 degrees on problematic aspects, including runout zones.

    A waist-high slab that was remotely triggered in Evan's Basin on Wednesday. The size of these avalanches will grow even further with higher elevations and/or more wind-loading. 

Avalanche Discussion

A Special Avalanche Bulletin has been issued for the weekend. Why, you ask?  The combination of hazardous conditions (deadly size with sensitive triggering) on a clear-sky day after a painfully powder-deprived season is a recipe for an accident.  Conditions for skiing, snowboarding, and machining are excellent, but the consequences of triggering an avalanche are deadly serious.  Several tragic accidents have occurred in recent days in California and Utah (1,2).

Weak layers on the north half of the compass have been thoroughly documented this season due to well-below average snowpack.  These weak layers just developed thick, well-connected slabs ranging from 2 to 4 feet thick (deeper on drifted terrain).  Forecasters have remotely triggered dangerous avalanches each day of the storm and documented a handful of very large avalanches (big enough to knock down trees and difficult for a person to survive).  You can look at this data for more details on the recent avalanche activity, but keep in mind that poor visibility has hampered documentation of natural avalanche activity.

The dangerous conditions cover the entire forecast area, and even below treeline terrain near town poses a deadly threat.  Multiple natural avalanches ran near town on Gibson Ridge, Peanute Lake Road, and Long Lake.  Forecasters remotely triggered a surprisingly large and widely propagating avalanche on Snodgrass Mountain yesterday.

Conservative decision-making is a must to stay safe this weekend.  You may or may not experience signs of instability before triggering a serious avalanche; don't let a lack of cracking or collapsing convince you otherwise.  Carefully manage overhead hazards, as you can trigger a deadly avalanche from below, and some slides may run much further than you expect.

Temperatures are forecasted to remain cool today, but strong solar radiation will slightly warm some sunny terrain features, making loose avalanches possible.  Expect an increase in loose avalanche activity as temperatures further warm on Sunday.

Regions covered