Bulletin d’avalanche

Snake River Range

Bridger-Teton Avalanche Center
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Danger d’avalanche

Wed
Alpin
4 · Fort
Limite forestière
4 · Fort
Sous la limite
3 · Marqué
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Périmé — ce bulletin a expiré 6 months ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

Very dangerous avalanche conditions will develop by this afternoon and evening due to heavy rates of snowfall today. Avalanches will be capable of breaking within the new snow and deeper on buried weak layers. Once enough snowfall accumulates, avoid riding on steep slopes and stay clear of steep terrain overhead where natural or remotely triggered avalanches can impact skiers and riders above 7,500’.

A Winter Storming Warning is in effect from February 24, 5:00am until February 25, 5:00pm.

Problèmes avalancheux

  • Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely
    Taille
    1.5–3

    Rapid loading of new snow and wind will add stress to buried weak layers formed during the month-long dry period in January. Previous slab depths have been around 2 feet and could increase to 3+ feet deep today based on the amount of snow that falls. The most dangerous terrain will be on N-NE aspects above 7,500' where we have seen the most avalanche activity. Both wind-loaded and sheltered terrain should warrant caution due to the spotty distribution of the buried surface hoar and weak facets. Avalanches can be triggered remotely from gentle terrain above, below, or beside steep slopes. Natural avalanches are possible by the end of the day. Give avalanche terrain a wide margin of safety to account for the unpredictable nature of these persistent slabs.  

    A large avalanche that was remotely triggered by a rider in the Snake on Saturday (2/21). This avalanche failed 2-3 feet deep on weak snow that formed during January.

    Photo: Bridger-Teton Avalanche Center

  • Storm Slabs

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

    Rapid rates of snow 1-2 inches per hour for the whole day will create unstable new snow. Snowfall totals of 10-16 inches of heavy, dense snow are possible by 5pm. This will make human triggered avalanches likely across all elevations, while slab depths will vary based on elevation. 

    Wind slabs: West to southwest wind 20-30 mph will form fresh wind slabs above 8500’. Slab depths will increase to 2+ feet by 5pm. Watch for active snow transport, shooting cracks, and stiffened new snow as a sign of fresh slabs forming on leeward and cross-loaded terrain. Wind loaded terrain will also make persistent slabs more likely on slopes that harbor buried weak layers.

Avalanche Discussion

A Forecast based on Forecasts

The severity of the avalanche danger will be directly related to the amount of snow that falls today. Snow amounts of 8-12 inches should warrant significant caution, creating unstable new snow and adding ~1 inch of snow water equivalent rapidly to buried weak layers. Avalanches have been triggered on the January drought layers the last 5 days despite any snowfall (check the recent avalanches here). Persistent slab avalanches will be possible today even before the new snow adds stress. Most of the avalanches have failed on buried surface hoar. The intense loading today could tip the scale and start producing more avalanches failing on the faceted snow from January. Snow above these weak layers will settle and become hard slabs today. For this reason, avalanches could be more widespread during this storm cycle. As previously seen, these avalanches are capable of breaking further upslope or cross-slope than expected and can fail after multiple riders have ridden a slope. 

Keep a close eye on the amount of new snow that falls today. Plan your backcountry route carefully to create a safe exit for when very dangerous conditions develop. As you experience rapid loading of snow in the backcountry, be aware that the danger is incrementally increasing. Enjoy the fresh snow, but don’t become complacent as the powder becomes deeper. Weird weather creates weird avalanches.

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