Bulletin d’avalanche

Transitional

Haines Avalanche Center
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Danger d’avalanche

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

Points saillants

10-15" new snowfall from the last 48 hours fell on top of a widespread crust and may not bond well. Look for recent avalanches, shooting cracks, or any whumpfing/collapsing signs that will indicate unstable condtions and slab formation. Be cautious and use wide wargins around any terrain greater than 30 degrees while avoiding runouts and terrain traps.

Problèmes avalancheux

  • Storm Slabs

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

    Above freezing temperatures up to 3,500- 4,000' due to an inversion at the end of the storm on 12/30 in the Transitional zone caused the formation of a thick ( 1" +/-), widespread "end of year" melt freeze crust.   New snow may form slabs on the crust bed surface by either deposition/settling or wind transport and will just need a trigger to complete the recipe for an avalanche.  

    Moderate-high uncertainty if and where a slab will form over this new weak layer.  Colder temps during and after the storm have kept the new snow dry and lacking slab characteristics as of yesterday.  Snow is readily available for transport for the moderate SE wind gust and the incoming N-NW winds.

     

Avalanche Discussion

The "end of year" melt freeze crust on the upper part of the snowpack is the main sliding surface suspect currently as new snow falls and is distributed on top.  But, a weak layer of facets rest below the crust have been observed. Distribution along with senstivity remain to be seen especially at elevations above treeline. Treat these slopes as guilty until proven innocent. The weak layers above and below the crust could have widespread propagation potential and need to be tracked going forward. 

Also, from earlier this season, and now more than a meter deep, a few melt-freeze layers are present throughout the snowpack at all elevations and aspects. These layers have mostly been found to be healing but could fail and produce an unlikely though larger avalanche. Our overall warmer and wetter temperature regime this season has helped slow the development of persistent weak layers (PWL's) in the snowpack. However at higher elevations and further inland these grain types can exist, and will require continued assessment. 

The people you go out with, the way you communicate, and the way you practice risk reduction as a team throughout the day is equally important as the conditions.

Help us gather information about weather, snowpack, and avalanche activity by reading and submitting field observations. Useful observations can be anonymous and include: 

  • Natural or human-triggered avalanche activity
  • Signs of instability: Cracking, collapsing, or whumphing
  • Red Flag Weather: Precipitation, wind loading, warming temperatures and rain-on-snow
  • Surface hoar growth, snow depth, persistent weak layers, etc
  • Snow stability tests, or pit result and location, elevation, aspect, etc 

Were you caught, carried, injured or buried in a slide? We are all human and can benefit from lessons learned, please report incidents to Haines Avalanche Center staff confidentially.

Régions couvertes