Avalanche forecast

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Haines Avalanche Center
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Avalanche danger

Alpine
3 · Considerable
Treeline
3 · Considerable
Below
2 · Moderate
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Highlights

The avalanche danger is CONSIDERABLE above 1,500 feet and MODERATE below. Yesterday's snow was accompanied by warm temps and moderate to strong S-SE winds that switched SW-W by afternoon and formed fresh wind slabs. Identify slopes that are greater than 30 degrees and use caution around convexities that may be loaded. Buried weak layers could be triggered from a shallow area, or from a large trigger like a cornice fall or wind slab. 

Avalanche problems

  • Wind Slabs

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

    Moderate to strong SE-S-SW-W winds transported yesterday's storm snow, forming wind slabs at mid and upper elevations on leeward aspects. Wind slabs can range from soft to hard, thin to thick, and are often smooth, rounded, and sometimes sound hollow. Today's fresh snow may make visual clues for wind-slab identification difficult.

    Consider the consequences of slopes with terrain traps, such as trees, gullies, and cliffs.  Even a small wind slab could lead to significant consequences in the wrong terrain and hard blocky debris could be harmful. Consider wind loading over persistent slabs where a surface slide could step down or be triggered by cornice fall (see Problem 2).

     

    (03/14/24)Wind affected the surface at Flower from yesterday's strong W wind. 

    Photo: Tim Thomas

  • Persistent Slabs

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

    Weaknesses within the snowpack are still present and demonstrating propagation potential. Remember wind loading and more precipitation increase the likelihood of persistent slab avalanches failing.  Use wide safety margins to manage the terrain and your group. Target these layers with stability tests and regard them as guilty until proven innocent. 

    Persistent slab avalanches often fail without warning signs, propagate wider than anticipated, and can be remotely triggered. They are a low feedback problem meaning you could ride the same slope numerous times until someone hits a shallow trigger point and initiates a slide. We can reduce the risks by incorporating conservative decision-making.

     

    (3/11/2024)

    Old Faithful-N-3400'.  Fair to poor structure,

    Photo: Haines Avalanche Center

Avalanche Discussion

Continue to keep you and your group's heads on a swivel with the current snowpack. Not seeing natural avalanche activity does not mean that you still couldn't trigger a slide. Keep close tabs on any red flag weather including precipitation rate, type, and intensity. Pay attention to warming temperatures, recent wind loading, and rain on snow. Mid-elevations are likely to prove the most difficult to assess due to fluctuating temperatures that have formed crusts and weak layers. 

Notable layers in the snowpack:

  • Recent snowfall accumulation & wind loading from 3/14
  • Northerly outflow wind event- 50-100cm deep-Protected = preserved, near-surface facets or "recycled powder" formed in terrain protected from wind.-Extreme winds formed wind slabs that are now buried persistent layers.
  • Valentine's warm inversion, down 80-120cm: mix of melt-freeze crust, buried surface hoar, and hard sun-warmed surfaces.
  • The late January Pineapple Express crust. An intense precip event saw pooling and percolation with warming to 5,000ft.
  • End-of-Year Crust (EOY). Wet and warm end of last year, freezing levels to 4,000ft.

  Early-mid March has historically come with avalanche accidents in our valley. As part of your trip plan, establish a mindset for your group before you venture into the mountains. This can help combat human factor bias and heuristic traps. Use weather, avalanche, and terrain checklists. Deploy ALPTruth:  

The ALPTRUTH acronym covers 7 contributory factors to avalanche accidents.  When reviewing over 1000 avalanche accidents, Ian McCammon found that 3 or more of these factors were present in over 90% of accidents.

  • A: Avalanche. Have there been any recent avalanches (within the last 48 hours)?
  • L: Loading. Has snow, wind, or rain loaded the slope in the last 48 hours?
  • P: Path. Will your planned travel path cross an obvious avalanche path? Will your uphill travel cross any potential avalanche paths?
  • T: Terrain trap. Is there a terrain trap? These include gullies, trees, cliffs, or other features. A slide into a terrain trap will increase the severity.
  • R: Rating. What does today’s avalanche report look like for your area? If there’s a rating of “considerable” or higher, you may want to reconsider.
  • U: Unstable snow. Have you heard any cracking, collapsing, whoomping? These are clear signs of instability.
  • TH: Thaw. Has there been recent warming of the snow’s surface due to sun, rain, or air temperature? Warming can increase instability and avalanche risk.

Thinking ahead:

  • When the next loading event happens, is it slow and incremental or rapid and significant?
  • What are the temperatures, steady and moderate, spring diurnal, or are freezing levels rising?
  • How does the likelihood of propagation increase or decrease with strength vs. structure?
  • Is there weak snow above or below a crust? How strong or brittle is the crust? Does the crust laminate well to layers above/below or not?
  • Could strong solar radiation or warming temperatures contribute to instabilities, including cornice fall?

Click here for a detailed season weather & snowpack history.

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. Take an avalanche course, and practice companion rescue often with your riding group. Every scenario is different, so it pays to be prepared.

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 can benefit from anonymous lessons learned. Please report incidents to Haines Avalanche Center staff confidentially.

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