Bollettino valanghe

West Slopes Central

Northwest Avalanche Center
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Pericolo valanghe

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

Very large wet and dry snow avalanches occurred naturally and with human triggers on Monday. Avalanches will become less likely as the storm passes, but expect to continue seeing avalanches Tuesday. Steer around steep slopes, and shift your travels so that you avoid lower angle terrain if it is beneath large avalanche paths. 

Problemi valanghivi

  • Wet Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Likely
    Dimensione
    2–3

    Several large and very large wet slab and wet loose avalanches were reported Monday.  Warm, wet conditions and a snowline hovering around 4000-4500ft means we've got a strange combination of a mostly dry snowpack with a variable mix of wet, heavy snow on top,  depending on the elevation you're at. This doesn't particularly categorize as your usual wet slab avalanche, but it still falls within the range. At lower elevations where rain saturated the snow, you'll find wetter and softer snow and more  typical wet slab avalanche problems. 

    As the snowpack is adjusting to all the water and weight added to it, possible natural avalanches and likely human-triggered avalanches will remain a concern on Tuesday. In addition to wet slabs, you'll probably also encounter wet loose avalanches on steep slopes.  Avalanches will most likely remain in the new snow layers, but they could run as deep as older underlying crusts or weak layers.  Keep your travel to slopes less than 35 degrees, and steer around the runouts of large avalanche paths, as natural avalanches are still possible. 

    An example of a wet slab avalanche failing above a crust.  Photo: Forest McBrian

  • Storm Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Likely
    Dimensione
    2–3

    At upper elevations where snow remained drier, expect to encounter reactive storm slabs.  It is likely that you could trigger an avalanche on one,  probably occurring within the new snow layers. There's a chance an avalanche could fail as deep as the new/old snow interface where we were previously finding weak layers, or possibly down to the Valentine's crust. Avalanches in deeper layers might mean avalanches as  deep as 3 to 5 feet at upper elevations. Where wind drifted slabs into thicker deposits, there is a higher chance of triggering an avalanche.  Plenty of wind accompanied the atmospheric river so there's a good chance you'll find wind slabs in your travels. 

    Don’t ignore obvious signs of instability like shooting cracks, whumphs, or recent avalanche activity.  Approach any steep slope with caution and remain aware of terrain above you. Stick to lower angle slopes, and steer around the bottoms of large avalanche paths.

    (2/20/2022)

    Recent reactive slabs that were easy to trigger in a neighboring zone.

    Photo: Alpental Pro Patrol

Avalanche Discussion

Neighboring zones reported very large, destructive avalanches on Monday. There were also an abundance of avalanches on smaller slopes and in lower angle terrain than where you would normally expect to see avalanches.  Conditions will slowly stabilize, but you could probably still encounter avalanches where you wouldn't normally expect to see them Tuesday. As of Monday evening, the storm totaled around 5 inches of water, equating to almost 3 feet of snow at upper elevations in the West Central zone, with another foot or more overnight Monday. This is a lot of water and snow, accompanied by warm temperatures and wind in a short period of time. Snow conditions are unusual, with wet snow and wind-affected surfaces.  We're on the heels of a large natural avalanche event and it's still not the time to get on steep slopes in the backcountry. Lower angle terrain can still make a good trip and see you making it home safely at the end of the day. 

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