Bollettino valanghe

West Slopes North

Northwest Avalanche Center
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Pericolo valanghe

Thu
Alta quota
3 · Marcato
Limite del bosco
3 · Marcato
Sotto il limite
3 · Marcato
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In sintesi

Avalanche danger will increase throughout the day Wednesday as new snow accumulates. Expect avalanche activity during periods of heavy loading due to new snow and wind. Minimize your exposure to overhead hazard and avoid open slopes 35 degrees and steeper.

Problemi valanghivi

  • Storm Slabs

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

    Expect 1-2ft of new snow over the next 24hrs with the heaviest snowfall rates during the day Wednesday. Avalanches could fail at the new/old snow interface or deeper and wider on the slick 12/21 crust below. Large human triggered avalanches are likely on slopes 35 degrees and steeper. If forecasted precipitation is exceeded, a natural avalanche cycle could occur at upper elevations late in the day Wednesday. New snow may not bond well to variable old snow surfaces including surface hoar and near-surface facets. The thickest and most reactive slabs will exist in leeward terrain at upper elevations. Be prepared to make observations as you travel and investigate the snowpack carefully. Use small slope tests and hand pits to observe the recent snow and determine which layers are most sensitive to triggers. Watch for recent avalanches, shooting cracks, and collapses, and seek out conservative and lower-angled terrain away from avalanche path run out zones.

    (12/28/2020) A large snowboarder-triggered avalanche on Shuksan Arm (NE, 5400ft). The avalanche broke 80-100ft wide and 1-2ft deep and slid on the 12/21 crust. The snowboarder who triggered the avalanche was the 6th rider on the slope and was caught and carried in the avalanche but uninjured. Photo: Colin Wiseman

Avalanche Discussion

Several human-triggered avalanches (D2) were reported the past few days including two near misses Monday on Shuksan Arm. Recent avalanches occurred in northerly terrain above 5000ft on convex slopes steeper than 35 degrees. A few remotely triggered avalanches were reported in similar terrain since Christmas, and some recent avalanches had impressive propagation. In some instances, avalanches occurred on slopes with previous tracks. Very few recent natural slab avalanches were reported.

All the recent avalanche activity is bull's eye data the snowpack is adjusting to the recent storm snow and still needs time to stabilize. Additional snowfall Tuesday and Wednesday will only stress the snowpack further and likely create avalanches. Uncertainty exists regarding the extent of weak snow associated with the 12/21 crust and the 12/25 interface. Incoming snowfall over the coming days will thicken existing slabs resting on these layers creating the potential for very large avalanches. Use the 12/21 crust as a prominent marker in the snowpack looking for sudden or propagation fractures in the snow above. 

During the ongoing Covid-19 pandemic, continue to follow the latest guidance from local, state, and federal health officials. Avoid unnecessary risks that could impact first responders and stress medical resources.  Wear a mask when appropriate, practice social distancing, and consider recreating closer to home.

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