Bollettino valanghe

Mt Hood

Northwest Avalanche Center
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Pericolo valanghe

Mon
Alta quota
3 · Marcato
Limite del bosco
3 · Marcato
Sotto il limite
2 · Moderato
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In sintesi

Slab avalanche hazards are expanding as Mt. Hood builds a snowpack. New snow combined with additional wind will expand the risk of widespread large avalanches in windloaded terrain into the near treeline zone. Ascend the terrain cautiously, choosing slopes less than 35 degrees anywhere you suspect windloading.

Preliminary Report: On Saturday morning, December 11th, an avalanche fatality occurred in Silver Basin area of Crystal Mountain Ski Resort. See the forecast discussion below for additional details.

Problemi valanghivi

  • Wind Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Likely
    Dimensione
    1.5–2.5

    Large slab avalanches such as the incident at Crystal Mountain remind us how quickly wind-loading and heavy snowfall can create large and unfortunately, sometimes fatal, avalanches. Uncertainty remains elevated with limited observations near and above treeline, but with an ongoing storm blasting Mt. Hood for 36-48 hours and nearly 3-4 ft from Wednesday to Sunday, proceed to upper elevation terrain with caution.  Look for firm, punchy snow layers which may be covered by lower-density snow in order to identify the problem and avoid wind-loaded slopes steeper than 35 degrees.

    (12/11/2021) This avalanche in the Crystal Mountain area caught a party of 6 tourers and unfortunately resulted in a fatality on 12/11.

  • Storm Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1–1.5

    In less wind-affected areas, the snowpack has grown rapidly and is just reaching a threshold for storm slabs. With 8-12" of snow arriving through Sunday evening, you'll need to evaluate the potential for reactive interfaces between successive waves of snowfall. Cutting under a very small steep test slope can provide excellent information about the reactivity of potential slab layers. Only venture onto slopes steeper than 35 degrees after you have evaluated these layers and found them to be healing.

    Example: A small Storm Slab that likely failed as temperatures warmed on Saturday 12/11.

    Photo: Vetta Mountain Guides

Avalanche Discussion

The snow has been piling up with 27-30" of snow depth in non-wind-affected areas. Most of that snow arrived since early Wednesday morning and fell primarily on dirt. At higher elevations, you might find some areas where the snow fell on the early December crust, created by a series of atmospheric river events that melted most early-season snowfall.

A public observation taken on the south side of Mt. Hood found reactive wind slabs on south-facing slopes near the treeline on Saturday.  NWAC forecasters and Pro Observers were in the Timberline area both Thursday and Friday. They reported similar conditions on both days. Several days of Moderate winds with occasionally strong gusts stripped snow off of many terrain features near and above treeline. The snow deposited in ravines and canyons where observers could easily trigger a shallow wind slab. NWAC forecaster Andrew Kiefer encountered challenging travel around little zigzag canyon on Thursday.  Below treeline, there was not enough snow to ride or warrant an avalanche hazard on Thursday, that coverage continues to increase rapidly.

 We're still in the midst of the first major storm cycle of the year. With snow coverage expanding, avalanches are likely to be larger and more widespread than on Saturday. The cooling temperatures will enable winds to blow the lower-density snow onto lee slopes and the sides of canyons/ravines where even a small avalanche can rake you through early season coverage and into terrain traps. The most dangerous conditions will be at upper elevations - in terrain similar to the location of an avalanche fatality in Washington State on Saturday. The Silver Basin Avalanche described below represents a large and surprising avalanche in wind-loaded terrain. It serves as a good reminder to dial back your terrain selection and collect information before considering terrain that may increase your risk.

Preliminary Report: On Saturday morning, December 11, a party of six backcountry tourers were traveling uphill in a closed section of the Crystal Mountain Ski Area known as Silver Basin. The party triggered a large avalanche on a N to E facing slope at approximately 6500’. While all members of the party were initially caught, four were partially or fully buried. A nearby party of two witnessed the event and immediately assisted in the rescue. Crystal Mountain Ski Patrol was also notified and responded to the scene. Unfortunately, one of the fully buried victims did not survive. NWAC and Crystal Mountain Ski Patrol will collaborate to conduct an investigation. Our deepest condolences to the family, friends, and community.

Uphill travel reminder: Check in with your local ski area this weekend regarding terrain access and parking updates. Closed ski areas often share a similar snowpack and avalanche hazard as the surrounding backcountry. You may also encounter other hazards like active avalanche mitigation, unmarked obstacles, snowmobiles, groomers, and other heavy equipment as ski areas prepare to open. Be prepared to make your own assessments and handle emergency situations.

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