Avalanche forecast

Haines Pass

Haines Avalanche Center
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Avalanche danger

Sat
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
2 · Moderate
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Highlights

The avalanche danger is MODERATE at all elevations. Cold temperatures over the past few weeks haven't helped heal weaknesses in the snowpack that still remain possible for human triggering. These persistent slab avalanche types can propagate widely and in unpredictable ways. This problem requires an increased margin for error and conservative terrain choices.

Avalanche problems

  • Persistent Slabs

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

    There are numerous buried persistent weak layers within the snowpack that cold temperatures have made worse. Persistent problems are tricky and may not provide obvious red flags- when triggered they produce destructive avalanches with wide propagation and 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 that fails on buried weak layers across terrain.  

    Probe while traveling to feel for strong over weak layering to help identify and assess the presence of these persistent layers. Talk to your partners about what terrain you should avoid, including overhead hazards, and connected terrain features. Travel one at a time to limit exposure. 

    Avoid hazards such as terrain traps like rocks, cliffs, trees, gullies and road cuts that could increase the consequences of being caught in a slide, or where snow could pile up quickly. The possibility of an avalanche stepping down is another reason to use wider safety margins at this time.

     (1/25/2024)

    Snow pit wall shows where weak faceted snow grains were easily excavated out at 4,200' S-SW Aspect Chilkat Pass Zone.

     

Avalanche Discussion

Sustained north winds this past week have created thick and thin areas of the snowpack. This spatial variability results in certain shallower areas being where you could still trigger a slide from as it propagates into deeper areas. The winds may have also drifted snow further downslope and created pockets that are susceptible to mid-slope releases. Identify and avoid traveling on or below steep terrain where the problem exists.

Freezing cold temperatures 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 it's thick and thin variability is dependent on duration and intensity of the warm and inverted EOY event. Very weak faceted grains have been observed around the EOY crust, and the cold is making them worse. 

Other layers to note are from earlier this season include a few melt-freeze layers that are present throughout the snowpack formed during other warming, or rain on-snow events. Recent observations have confirmed a noteworthy December 24th Christmas Eve crust located down 60-90cm from when freezing temperatures reached ~3,000ft. 

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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