Boletín de aludes

Lutak

Haines Avalanche Center
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Peligro de aludes

Alta montaña
3 · Notable
Límite del bosque
2 · Moderado
Bajo el límite
1 · Débil
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Desactualizado: este boletín caducó 3 years ago. Estás viendo condiciones pasadas, no el boletín vigente.

Lo esencial

The avalanche danger is CONSIDERABLE above 2,500ft and MODERATE above 1,500ft. Strong northerly winds are re-distributing snow and building sensitive wind slabs at mid-to-upper elevations. Look for signs of blowing snow, and avoid recently loaded slopes in any terrain greater than 30 degrees including run-out zones. Frigid temperatures and hard refrozen snow surfaces are other current hazards.

Problemas de aludes

  • Wind Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Likely
    Tamaño
    1–2

    Look for visible transport of snow and avoid terrain where wind slabs have been built up on slopes greater than 30 degrees. Northerly winds have been blowing snow from one aspect to another mostly loading E-SE-S aspects, however, expect to find them in all terrain.

    Shooting cracks, collapsing, and areas of more cohesive snow formed by the wind are indicators you are on a wind slab. With how strong the winds are wind slabs can form well below a peak or ridge down the slope and at mid-elevations.

    Use careful terrain identification to bypass slopes that could slide and areas where you could trigger a slide from below. Give yourself wide margins for error if you are traveling around wind slabs.

    Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard.

Avalanche Discussion

Last weekend, we got walloped by a warm and wet pineapple express event that brought 2-3"+ of snow water equivalent (SWE) Jan 26-28, with freezing levels peaking up to 5,000'. This was when the 21-mile Slide Path slid across the Haines Hwy. Then Monday, Jan 29th, was followed by another 2-3"+ of SWE in 24 hours with freezing levels around 2,500-3,000'. This was all accompanied by moderate gusting strong S-SE winds.

Cold temperatures most of January accelerated the weakening of snow grains throughout the snowpack: at the surface, below wind slabs, and above and below melt-freeze crusts. We should treat these layers as guilty until proven innocent and continue to monitor, track, and assess stability on a slope-by-slope basis. Melt-freeze crusts are a dangerous weakness in a snowpack and have played a role in multiple avalanche accidents, even within our forecast zones.

What we know about the EOY crust is that above-freezing temperatures  ~3,000ft- 4,000ft on December 30th caused the formation of a thick ( 1" +/-), widespread melt-freeze crust down 20-50cm. The strength of this layer and its thick and thin variability depend on the duration and intensity of the warm and inverted EOY event. Very weak faceted grains have been observed around the EOY crust, and the cold made them worse. 

Other layers to note are from earlier this season, including a few melt-freeze layers present throughout the snowpack formed during other warming or rain-on-snow events.

The people you go out with, how you communicate, and how you practice risk reduction as a team throughout the day are equally important as the conditions. The wide propagation and dangerous nature of persistent slabs are best mitigated with safe travel techniques and terrain management- only exposing one person to a slope at a time, avoid grouping up in run-out zones, and re-consider islands of safety to truly limit your group's exposure. 

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.

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