Bulletin d’avalanche

West Slopes Central

Northwest Avalanche Center
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Danger d’avalanche

Wed
Alpin
4 · Fort
Limite forestière
4 · Fort
Sous la limite
4 · Fort
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Points saillants

A natural avalanche cycle is expected over the next 24 hours as heavy snow, wind, and rain impact the West Central Zone.  Avalanches could grow large enough to bury and destroy a car or break mature trees. Conditions will be dynamic and unmanageable Tuesday, and travel in avalanche terrain is not recommended. 

Problèmes avalancheux

  • Storm Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Very Likely
    Taille
    2–3

    Heavy snowfall will bring 1-2ft of new snow by Tuesday morning. Temperatures will rise throughout the day as heavy precipitation continues. Above the rain,  new and wind loaded snow will create slabs several feet thick. Natural avalanches could run far distances and grow very large. Avalanche danger will rise and peak during times of heavy snow and warming temperatures. The new snow will need time to settle and stabilize. Avoid avalanche terrain Tuesday as the snowpack adjusts to this heavy loading event. 

    (12/22/2020) Example photo of the crown of a very large slab avalanche in alpine terrain on the west face of Mt. Shuksan. Photo: Adam U

  • Glide Cracks

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely
    Taille
    2–3

    Rain will rapidly destabilize the snowpack Tuesday. Wet avalanches will likely run naturally and may act in surprising ways. Some uncertainty exists as to which type of wet avalanche will occur. Whether it be glide, wet loose, wet slab, or all three, conditions will be very dangerous as the snowpack gets saturated with heavy rain up to 6000ft. These avalanches are difficult to predict and even harder to assess. Build in a wide margin for error if you choose to venture out during the storm.  Being caught in a wet avalanche Tuesday would have devastating consequences. Even wet loose avalanches could build significant mass as they run downslope and pack quite a punch. Avoid travel in or below avalanche terrain and steer clear of avalanche path run out zones.

    (1/3/2021) A very large glide crack below treeline in the Anderson/Watson area above Baker Lake. This glide crack opened during the rain event on January 1 when 3.5in of rain fell up to 5000ft. Photo: Tom Shields

Avalanche Discussion

A strong atmospheric river event will bring a surge of moisture to the Central Cascades through Wednesday. The heaviest precipitation and strongest winds will occur Tuesday. Large avalanches are expected in many areas. Snow will fall through Tuesday morning before a warming trend drives snow levels well up into the alpine. Expect a mix of dry and wet snow avalanche problems and very dangerous conditions at all elevations. Above 4500ft, new snow from Monday night and cold, dry snow from last week will experience rapid thaw with several inches of rain. The storm will bring heavy winds and feet of snow high above treeline where cornices will continue grow and sag, acting as huge triggers on slopes below if/when they fail. Only venture out Tuesday if you are confident in your ability to avoid avalanche terrain. It may be a good time to wait out the storm and let mother nature run its course. 

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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