Avalanche forecast

Haines Pass

Haines Avalanche Center
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Avalanche danger

Alpine
2 · Moderate
Treeline
2 · Moderate
Below
2 · Moderate
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Out of date — this forecast expired 3 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

The avalanche danger is MODERATE on all aspects and elevations.  Slopes greater than 30 degrees could be difficut to trigger but have unexpectedly wide propagation with high consequences. Use visual clues to identify and avoid terrain such as starting zones, run outs, and terrain traps. Cold temperatures are an additional hazard and slow any emergency response.

 

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Unlikely
    Size
    1–3

    This week's winds created slabs over widespread persistent weak layers. When persistent layers fail, they produce destructive avalanches with wide propagation. Human-triggered avalanches are unlikely, but would have high consequences.  

    Buried under the wind slabs are a combination of weak surface snow, or near-surface facets from last week and surface hoar that formed Jan 6-7th.  Cold temperatures are making it worse by driving the weakening of snow grains, known as faceting.  Faceting is happening in last week's persistent weak layers AND deeper into the pack snow around melt-freeze layers. 

    Persistent slab avalanches are not a problem to try and outsmart. Slopes greater than 30 degrees have the potential to propagate an avalanche from a thin area of snow to a deeper one- without any warning signs.  Talk to your partners about what terrain you should avoid and where you are most likely to initiate a slide from. Travel one at a time to limit exposure to slopes on the way up and down.  Snow that is getting denser and more consolidated is a clue that you are venturing out on a slab, also shooting cracks and collapsing/whumphing are indicators too.

    Avoid hazards such as terrain traps like rocks, cliffs or trees that could increase the consequences of being caught in a slide, or where snow could pile up quickly. With mulitiple weak interfaces,  the possibility of an avalanche stepping down from one layer into another is a reason to use wider safety margins at this time.

    Cold temperatures are driving faceting above and below the End Of Year (EOY) crust located 1-2ft deep. Due to this crust being elevation dependent there is a high degree of uncertainty as to how the reactivity has changed over this past week.

Avalanche Discussion

The intensity of faceting this week will produce a highly unstable sliding surface depending on the next loading event (wind, snowfall, warming, rain, etc.)  

Freezing cold temperatures are accelerating 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 ~3,000'- 4,000' on December 30th caused the formation of a thick ( 1" +/-), widespread melt-freeze crust.  The strength of this layer and it's thick and thin variability is dependent on duration and intensity of the warm and inverted EOY event. Weak faceted grains have been obersved around the EOY crust, and the cold is making them worse. 

Other layers to note are from earlier this season, and are now more than a meter deep. These include a few melt-freeze layers that are present throughout the snowpack at all elevations and aspects. These layers formed during other warming, or rain on-snow events and have mostly been found to be healing but could fail and produce a very unlikely though larger avalanche. Our overall warm and wet temperature regime through the 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 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. 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.

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