Avalanche forecast

Haines Pass

Haines Avalanche Center
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Avalanche danger

Alpine
3 · Considerable
Treeline
3 · Considerable
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Out of date — this forecast expired 3 years ago.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 CONSIDERABLE above 1,500' and MODERATE below that.  Look for signs of wind loading including drifted pockets of snow,  stiff snow that sounds hollow, shooting cracks, or collapsing. Be especially careful to avoid terrain traps with large amounts of snow above them. With weak persistent layers buried in the snowpack, keep margins wide to account for the potential of step down avalanches. 

 

 

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–2

    You are mostly likely to trigger a slide where there has been wind loading.   Strong sustained north-northwest outflow winds may have unusual loading patterns that transported snow further down the slope than normally suspected, even in steep gullies or down in the trees.

    Look for shooting cracks, whumphing or collapsing that indicate unstable wind slab conditions.  Visually identifying the characteristic shapes and textures from wind effect can also help you avoid wind slab prone slopes. Protected could mean preserved! When looking for non-wind affected terrain, be aware of the potentially weak structure below.  (See problem #2) 

    (1/18/2024)

    Strong winds transporting snow on the Chilkat Pass 

  • Persistent Slabs

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

    Now buried are numerous persistent weak layers such as near-surface facets and surface hoar that formed Jan 6-7th, and melt-freeze crusts like the end of year (EOY crust.) Cold temperatures are making things worse by driving the weakening of snow grains near the surface and around these persistent layers throughout the snowpack. 

    Persistent problems are tricky and may not provide obvious red flags- when triggered they produce destructive avalanches with wide propagation and 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.

    (1/13/2024)

    Above the glove is the EOY crust and below is the Christmas Eve crust. The snow around these crusts was rotten and easily brushed away.

    Photo: Jeff Moskowitz

Avalanche Discussion

As cold temperatures create new near surface facets (NSF) or weak snow, they could facet enough to become snow available for transport- producing fresher, more tender wind slabs. We should treat the multiple weak layers as guilty until proven innocent and continue to monitor, track, and assess stability on a slope-by-slope basis. 

Freezing cold temperatures are 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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