Bulletin d’avalanche

Tetons

Bridger-Teton Avalanche Center
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Danger d’avalanche

Mon
Alpin
3 · Marqué
Limite forestière
3 · Marqué
Sous la limite
Sans niveau
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Périmé — ce bulletin a expiré 3 years ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

Today, it will be possible to trigger a large avalanche that can bury a person. Avalanches reported yesterday are proof of this. Additional snow and wind will contribute to dangerous conditions. Conservative decision-making and low angle terrain choices are critical in order to stay safe.

Problèmes avalancheux

  • Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    1–2.5

    Triggering a hard slab avalanche 2-4 feet deep is possible in steep terrain. These avalanches are most likely to occur above 8,000’ on slopes that face away from the sun (W-NW-N-NE-E). However, any steep slope that held snow prior to the 12/1 storm should be approached with caution as the structure is likely poor. The November drought layer is now buried about three feet deep above 9,000’. As a result, triggering one of these avalanches is becoming slightly more difficult and may not occur until you have committed to the slope. If you do collapse the weak layer, the resulting avalanche will likely be large.

    Digging and probing are great ways to evaluate the snowpack. If you press your ski pole through the snowpack and it suddenly drops with little resistance, then chances are you’ve found a location where triggering a persistent slab avalanche is possible. While evaluating the snowpack can help identify problem areas, persistent slabs are unpredictable and dangerous. The best way to avoid triggering a large avalanche is to steer clear of steep terrain all together today.

    (12/5/2023)

    This large remotely-triggered avalanche illustrates the current problem.

  • Wind Slabs

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

    Mountain top winds picked up overnight and are blowing consistently in the mid 20’s (mph) out of the west/southwest. Loose, low density snow was found on many slopes yesterday and has the potential to be transported by increasing wind speeds. Additionally, new snow accumulation of up to 7 inches is expected by this afternoon/evening. Newly formed wind slabs with depths up to one foot are possible in the upper elevations by the afternoon. Watch out for areas where the snow feels “thicker” or “punchy” and avoid terrain with obvious wind drifts. It is possible that a wind slab triggered on the surface could step down to weak layers buried deeper within the snowpack resulting in a large avalanche.

    (12/7/2023)

    D1 avalanche at the top of Twin Slides triggered remotely on a wind loaded pocket that propagated 30 feet wide and ran 400 feet. 9700' S aspect

    Photo: Alex Drinkard

Avalanche Discussion

Over the past 10 days, two separate storms have deposited roughly 45” of snow with 3.8” of snow water equivalent (SWE) on top of weak, faceted snow that formed during the November drought. These loading events have added a great deal of stress to buried weak layers resulting in numerous natural and human triggered avalanches. Large (D2) avalanches have been reported nearly every day since the storm cycles began. While obvious signs of instability such as cracking and collapsing have decreased in frequency, avalanche conditions remain dangerous. Don’t be fooled, the snowpack is just waiting for a trigger. Skier and snowmobiler triggered avalanches reported yesterday in Moose Brush and Mosquito Creek are proof of this.

Additional snow and wind expected today will continue to push the buried weak layers towards the tipping point. This large natural avalanchethat occurred in Cody Bowl during the most recent storm (12/8) is an example of a location where the snowpack was recently pushed past the breaking point. Furthermore, any wind slabs that are triggered in today’s snow have the potential to step down to deeper and more destructive layers. Cautious route-finding and conservative terrain choices are critical to stay safe today. The only surefire way to avoid triggering a dangerous avalanche is to steer clear of steep terrain (greater than ~30 deg), especially where it is rocky and rolls over like a basketball. Seek out ridges and low angle slopes to maximize safety and enjoyment.

Régions couvertes