Lawinenlagebericht

Haines Pass

Haines Avalanche Center
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Lawinengefahr

Hochgebirge
4 · Gross
Waldgrenze
4 · Gross
Unterhalb
4 · Gross
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Kernpunkte

The avalanche danger is HIGH at all elevations. Increasing temperatures, strong winds, heavy precipitation, and rain on snow are all adding stress to buried weak layers. With the prolonged wet and warm weather, elevations below 2,500' are very likely to see wet slab releases. Due to the potential for large destructive avalanches, avoid all avalanche terrain, including overhead hazards, terrain traps, and run-out zones.

 

Lawinenprobleme

  • Persistent Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Very Likely
    Größe
    1–3

    The possibility of large destructive avalanches continues to increase. 2-3" of snow water equivalent (SWE) is forecasted in a 24-hour period today- with freezing levels reaching over 3,500'. Elevations below that have been saturated enough with water over the weekend that the likelihood of wet slab avalanches is increasing (see problem 2). This is a solid reason to avoid avalanche terrain altogether at this time. 

    There are numerous buried persistent weak layers within the snowpack at all elevations and all aspects. Slopes greater than 25 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. Hazards such as terrain traps like rocks, cliffs, trees, gullies, and road cuts increase the consequences of being caught in a slide or where snow could pile up quickly. 

    Expect an ongoing natural avalanche cycle through Monday with increased temperatures and freezing levels, heavy precipitation, strong winds, and rain on snow. 

     (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.

     

  • Wet Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Very Likely
    Größe
    1–3

    Rain and multiple days of above-freezing air temperatures can melt and destabilize the snowpack. We have now had multiple days in a row of rain on snow, with precipitation totals ranging from 2-3" of SWE and freezing levels reaching up to 3,500'. Wet slabs are the release of a cohesive layer of snow (a slab) caused by meltwater weakening the bond between the slab and an underlying weak layer.

    They can break widely and without clear warning signs.  Because the timing and amount of meltwater draining into buried weak layers vary significantly from slope to slope, there is a high amount of variability and uncertainty in predicting wet slabs.  The high-consequence nature of this problem and the increased likelihood of warming and precipitation intensity are reasons to avoid avalanche terrain currently, including run-out zones and overhead hazards until temperatures drop below freezing.

     

Avalanche Discussion

Warming temperatures, increasing freezing levels, heavy precipitation, strong winds, and rain on snow continue to play a role in increasing the avalanche hazard. Across all our forecast zones, on all aspects and elevations are buried persistent weak layers that could become more stressed and lead to an increased likelihood of human triggering along with a natural avalanche cycle, including roof avalanches.  

Last week, sustained north winds created thick and thin areas of the snowpack. This spatial variability results in certain shallower areas where you could still trigger a slide from as it propagates into deeper areas. The winds may have also drifted snow further downslope, creating pockets susceptible to mid-slope releases.

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 include a few melt-freeze layers 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 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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