Bollettino valanghe

Transitional

Haines Avalanche Center
Vedi sulla mappa

Pericolo valanghe

Alta quota
4 · Forte
Limite del bosco
4 · Forte
Sotto il limite
4 · Forte
Open full map
Non aggiornato — questo bollettino è scaduto 2 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

The avalanche danger is HIGH at all elevations. Forecasted precipitation amounts and rates are significant, with about 1.5" of water in less than 24 hours and strong SE winds. This rapid loading will likely cause persistent slabs deeper in the snowpack to release and, depending on the elevation of freezing levels, create storm slabs. Travel in avalanche terrain is not recommended including runout zones. 

Problemi valanghivi

  • Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Likely
    Dimensione
    1–3

    Weaknesses within the snowpack are present, and rapid loading will likely cause them to fail. Due to the large mass of snow involved, persistent slab avalanches are very destructive and dangerous. They often fail without warning signs, propagate wider than anticipated, and can be remotely triggered. Rapid precipitation, wind loading, and warming increase their likelihood. 

    With this tricky problem, it is important to stay off of and out from underneath slopes greater than 30 degrees and to use wide margins around run-out zones. Even small slopes should be avoided, especially when terrain traps are present, such as trees, rocks, and cliffs, or where snow could pile up quickly. The new snow needs time to stabilize and bond to other layers.

    (3/11/2024)

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

    Photo: Haines Avalanche Center

  • Storm Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Very Likely
    Dimensione
    1–2

    Storm slabs can be released as wet or dry, depending on the freezing level, and are most sensitive during and right after snowfall.  Temperatures are forecasted to warm during the day, with freezing levels around 2,500 feet.  The incoming bands of precipitation over the next few days will add an additional load on the persistent slabs (see Problem 1.) 

    Moderate winds gusting strongly from the S-SE will load leeward slopes,  so be wary of this drifting that could amplify the size of a slide. Don't underestimate the consequences of terrain features big or small. Even shallow storm slabs are dangerous on larger terrain features or slopes with terrain traps, such as trees, gullies, and cliffs.  

    Storm slabs can include dry loose snow or "slough" where even a small slide in consequential terrain could be dangerous or wet slides. 

Avalanche Discussion

Notable layers in the snowpack:

  • Recent snowfall accumulation
  • 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.

Regioni coperte