Bollettino valanghe

Northwest Mountains

Crested Butte Avalanche Center
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Pericolo valanghe

Sun
Alta quota
3 · Marcato
Limite del bosco
3 · Marcato
Sotto il limite
3 · Marcato
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In sintesi

The snowpack is slowly adjusting to the tremendous load from the Thanksgiving storm, but conditions remain dangerous on west through north through southeast slopes.   Avalanche crowns and debris piles across the landscape keep the danger at the forefront of your mind.  Conservative terrain selection is your best defense; keep slope angles around 30 degrees or less.  Lower elevation southerly slopes offer a less risky snowpack. 

Problemi valanghivi

  • Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Likely
    Dimensione
    1.5–2.5

    A significant avalanche cycle occurred on Tuesday and Wednesday following a major winter storm. Many of these avalanches were breaking 2 to 4 feet deep and releasing on weak faceted snow that formed earlier this winter. The upper snowpack is gaining strength, and this will decrease the obvious signs of instability in some areas as this avalanche problem slowly becomes more difficult to trigger. The most problematic aspects face west, north, east, and some southeast-facing slopes. The current travel advice is to avoid this avalanche problem. An effective way to avoid this problem is by traveling on low-angled slopes less than about 30 degrees that are not connected to steeper slopes above.

  • Wind Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1–2

    An increase in wind speeds on Friday, 11/29, continued overnight.  West and northwest winds transported snow to leeward terrain features at upper elevations.  Fresh drifts will be most common above treeline, and may extend to some near treeline ridgelines.  The most suspect aspects for encountering a recently formed Wind Slab are easterly and southerly slopes.  Avoid leeward terrain features at upper elevations where you encounter blowing snow, feel stiffer surface snow, or see smooth, lens-shaped deposits. 

    Drifting snow is visible in the background ridge and likely formed a fresh round of Wind Slabs at upper elevations.

    Photo: Eric Murrow

Avalanche Discussion

Snowpack observations before the Thanksgiving storm and documented natural avalanches during and after the storm clearly show the most problematic aspects and elevations; the most troublesome slopes face west through north through southeast.  If you choose to travel on terrain highlighted by the Persistent Slab distribution rose, your simplest and safest option is to travel on lower angled slopes not directly below or connected to steep slopes above.

Many slopes avalanched during the storm, and this removed the problem on some of these slopes by eliminating the slab component.  However, you must exercise caution if you attempt to play on avalanche bed surfaces and be certain of the extent of prior avalanche activity.  Some paths clearly avalanched full width, while others are hard to understand.  There are likely pockets of intact snowpack scattered throughout the terrain that must be avoided and thoughtfully managed.

If your terrain choice steers you away from the Persistent Slab problem, then you'll manage fresh Wind Slab formation on southerly slopes.  Blowing snow was observed across the forecast area on Friday and may continue into Saturday.  Thoughtfully read the snow surface to identify and avoid where these fresh drifts formed in open terrain at upper elevations.  You can find a less risky snowpack on lower elevation southerly slopes where recent drifting is unlikely. 

The first "Weekly Summary" is available now.  This first edition covers the months of October and November, including the Thanksgiving Storm.  Get up to speed on this winter's snowpack by clicking the "Weekly Summaries" tab just below the Bottom Line.

 

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