Bulletin d’avalanche

Gunnison

Crested Butte Avalanche Center
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Danger d’avalanche

Wed
Alpin
2 · Modéré
Limite forestière
2 · Modéré
Sous la limite
1 · Faible
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Périmé — ce bulletin a expiré 2 years ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

The most likely places for you to trigger a slab avalanche are on leeward terrain features at upper elevations.  Gusty west-to-southwest winds have been blowing snow for several days, with some of the strongest gusts occurring last night.  Carefully read the terrain, identify places with recent loading, and avoid slopes where you find signs of recent drifting.  Most triggered avalanches will only involve recent storm snow, but there is a lingering low probability that an avalanche will break deeper in the snowpack.  Wind-sheltered terrain offers lower-risk options.

Problèmes avalancheux

  • Wind Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    1–1.5

    Up to 9 inches of snow accumulated in the past few days. Recent westerly winds averaged in the 20 to 30mph range with notably stronger gusts near and above 12,000ft.  Above treeline slopes are the most likely places to encounter the problem, but some near treeline slopes may have the problem.  The specific locations to keep an eye out for new slab development would be on the leeward sides of ridgelines and in crossloaded gullies. Consider utilizing small test slopes to help identify the potential size and how reactive this avalanche problem is in your area.  Aspects and elevations that overlap with the Persistent Slab problem represent the areas where a 'step-down' avalanche is an outside possibility.

    An example of shooting cracks along a wind-loaded ridgeline from earlier this winter.  Signs of instability like this indicate unstable snow.

  • Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Unlikely
    Taille
    1–2

    Old hard slabs up to several feet thick have become isolated and difficult to trigger. You are unlikely to see signs of instability before triggering an avalanche that breaks on old, weak layers. The most likely trigger points would be where these hard slabs thin near their margins, on convexities, or near rocky areas. Recent snowfall and wind drifting may have obscured the surface clues, making identification of old, hard slabs difficult.

    This hard slab was triggered near Pearl Pass on 2/3.  This location is just beyond the CBAC's Southeast Mountain forecast boundary. 

    Photo: CAIC

Avalanche Discussion

Monday delivered another 1 - 2 inches of snow around the area, pushing storm totals up to 9 inches for some snowfavored locations over the past few days.  Areas at lower elevations near the town of CB snagged just a couple of inches during this timeframe.  Winds continued to hum, with some of the strongest gusts occurring overnight.  Irwin Guides Ridge Top station (Northwest Mountains) and the Carbonate Station (Southeast Mountains) recorded winds between 25 - 35 mph and gusts in the 50 - 60 mph range last night.  The weather continues to load leeward terrain features through small amounts of new snow and strong wind speeds.

Wind Slab avalanches are the most likely problem for you to encounter.  Alpine slopes have likely seen the most drifting, with fewer slopes in the near treeline elevation band developing slabs.  However, some near treeline slopes had very soft, faceted surfaces before the recent snowfall and wind. This creates a potentially sensitive avalanche problem where you encounter a fresh drift over soft, faceted old surfaces.  To avoid triggering a slab avalanche, carefully make sense of the loading patterns in the area you travel and avoid terrain with recent drifting.

The old Persistent Slab problem is unlikely due to an isolated nature across the landscape and a difficult-to-trigger sensitivity.  You can find old, hard slabs of snow below ridge tops, cross-loaded in gullies, and pressed into concave features.  Several Persistent slab avalanches were recently triggered regionally (Marble, Aspen, Tincup Pass).  Although an unlikely problem, this slow trickle of evidence suggests old, hard slabs remain an issue for backcountry travelers.

Looking to the future, a small storm will drop a handful of inches tonight, slowly ratcheting up the avalanche hazard as new snow accumulates above well-developed weak layers. A potent storm could arrive on Thursday night and may drop feet of snow over a few days. If weather forecasts are accurate in the coming days, be prepared to dramatically change your travel habits as the avalanche danger shoots upward. 

Upcoming Event - Open the storm floodgates with the Floodgate Operators at the Public House on Saturday, February 15. Tickets available here https://publichousecb.com/show/floodgate-operators-fundraiser-for-cbac/.  Proceeds from the show to benefit the CBAC.

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