Boletín de aludes

Lutak

Haines Avalanche Center
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Peligro de aludes

Alta montaña
3 · Notable
Límite del bosque
3 · Notable
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 1,500ft. Recent storm snow has formed cohesive slabs due to precipitation, warming, and wind making human-triggered avalanches likely. Confidence is high that the new snow is resting over a variety of persistent weak layers and a widespread hard bed surface that requires extra caution. Identify and avoid slopes greater than 30 degrees where a slab could propagate across terrain or entrain additional snow, making it difficult to escape from or pile up deep in a terrain trap.

Problemas de aludes

  • Persistent Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Likely
    Tamaño
    1–2.5

    A total of 8-15" of new snow has fallen over our region since Friday and is resting over widespread weak layers and a hard bed surface. Overnight precipitation, wind, and warm temperatures added more load and could easily be stressed and triggered by a rider today. Use terrain identification to avoid slopes steeper than 30 degrees including terrain traps and run-out zones. Expect the problem to amplify where larger patches of avalanche terrain can entrain larger amounts of snow. Be weary on the lee side of ridge tops and terrain features like gullies.

    Keep an eye out for wind-drifted snow by looking for texture and hardness changes. Use small test slopes with low consequences to assess how the new snow is bonding and make continued observations as you change the aspect and elevation.  Weak layers may be more or less apparent in certain areas which makes it tricky when mapping the problem.  Signs of instability include cracking, collapsing, hollowness, and cohesive surface snow. Utilize cautious route-finding and minimize exposure by traveling one at a time.

    Weak layers can continue to produce avalanches for days, weeks, and even months making them especially difficult to predict. It is important to remember that we are not dealing with a normal storm slab that may stabilize overnight. Slabs have the potential to pull back to lower-angle terrain and you can remotely trigger a slide from the bottom of a slope, or through connected terrain. Careful slope-to-slope assessment and conservative decision-making are essential, you don't want to get surprised!

    A unique stretch of clear, cold weather with very little wind at the end of last week produced rapid growth of near surface facets and surface hoar that act as persistent weak layers when buried. New snow from the weekend now blankets these weak layers on mountain slopes waiting for a trigger to cause an avalanche. Extra caution is warranted.

Avalanche Discussion

Below this fresh, beautiful snow are unusually widespread weak layers and a hard bed surface. This past week calm winds, clear days/nights, and cold temperatures created new persistent weak layers over a widespread hard melt-freeze crust. ☠️❄️‼️. These include weak snow, like surface hoar and near-surface facets. Powder fever can hinder judgment and requires patience to know how exactly/if the slab and weak layer are bonding.   

The natural avalanche cycle on Jan 27-28 released a variety of persistent slabs up to size 3.5 that have been observed at all elevations, aspects, and forecast zones. Most crown lines have been refilled from snow accumulation on Jan 29th or shortly after by winds redistrubuting snow. The increased freezing levels accompanied by heavy precipitation created a strong, widespread layer when the temperatures dropped below 0F Feb 2nd-3rd.

Numerous weak and faceted layers exist in the snowpack and are getting worse. These persistent weak layers are below strong melt-freeze crust layers. In the near term, the layers are very unlikely to trigger, but that could change with increased precipitation, temperature, wind loading, or sun. We need to continue monitoring as we enter into spring, and in extreme terrain, and around unsupported slopes.

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. Always practice 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. Carry radios, first-aid, and a two-way emergency communication device.

 

Recent weather history and snowpack layering:

  •  Feb 2-3rd - Light snow over our regions with the highest accumulations near town with 3-5".
  • Jan 31st-Feb 3rd - An intense northerly outflow event brought W-NW-N wind through the region. This was accompanied by another sharp drop in temperature with a maximum low of -15F at the Haines Pass. Another flip-flop weather event saw temperature increase between 25-40 degrees Fahrenheit.
  • January 27-29th - A two-pulse pineapple express event with ~6" total SWE(snow water equivalent.) During the first wave, Jan 26-28th, 2-3" of SWE fell as temps climbed, with freezing levels peaking up to 5,000'. This was when a D3.5 slid over the Haines highway at 21 miles.  In part two of the event on Monday, Jan 29th, there was another 2-3"+ of SWE, but in 24 hours, it was colder with 2,500-3,000' freezing levels and moderate to gusting strong S-SE winds. Both these events helped create the current widespread melt-freeze surface crust. 
  • January 2024 - Cold temperatures most of January faceted and accelerated the weakening of persistent snow grains throughout the snowpack: at the surface, below wind slabs, near melt-freeze crusts, and on the ground, especially in areas with a shallow snowpack. Three major temperature dips occurred around Jan 11th, Jan 19th, and Jan 22nd.
  • December 29th - The end of the year (EOY) melt-freeze crust is from when above-freezing temperatures  ~3,000ft- 4,000ft or higher caused the formation of a thick ( 1" +/-), widespread melt-freeze crust down 20-50cm. The cold weather in mid-January faceted and weakened snow around the crust. The "late-January pineapple express" had avalanches that released EOY instabilities in some areas but inconclusive in others.

 

 

Help us gather information about weather, snowpack, and avalanche activity by reading and submitting field observations. Useful observations can be anonymous and include: 

  • Avalanche Activity: Natural or human-triggered
  • Signs of Instability: Cracking, collapsing, or whumping
  • Red Flag Weather: Precipitation, wind loading, warming temperatures and rain-on-snow
  • Persistent Weak Layers: Surface hoar growth, snow depth, persistent weak layers, etc
  • Snow Pits: Stability test results, layers of concern, total snow depth, location, elevation, aspect, etc 

 

Were you caught, carried, injured, or buried in a slide? We are all human and can benefit from anonymous lessons learned. Please report incidents to Haines Avalanche Center staff confidentially.

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