Bollettino valanghe

West Slopes North

Northwest Avalanche Center
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Pericolo valanghe

Wed
Alta quota
4 · Forte
Limite del bosco
3 · Marcato
Sotto il limite
2 · Moderato
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In sintesi

A sizeable overnight avalanche cycle is expected to continue into the day Tuesday. Several inches of water Monday night will slightly taper into Tuesday but the snowpack will remain reactive for a little longer. Avoid steep slopes at lower elevations but if you venture higher steer clear of all avalanche terrain, including lower-angle slopes beneath large paths. 

Problemi valanghivi

  • Wet Slabs

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

    Wet slab avalanches are spooky and unpredictable. They usually happen when least expected, and are nearly impossible to escape. Three inches of water is forecasted for Monday night, falling as rain up to 8500ft. Water will percolate down into the snowpack, and large natural wet slab avalanches will result. Peak activity will probably happen overnight but avalanches will likely continue during the day as water travels deeper into the snowpack. Larger and more reactive avalanches are expected to occur in the upper elevation band. Further down, rain began sooner and the snowpack is shallower so activity is expected to decrease as you drop in elevation.  If you venture out, keep in mind there are a lot of uncertainties around the current snowpack and how it will react to all the recent water, so exercise more caution than you normally might during your outing.

    (1/14/2022)

    Example photo: A natural wet slab avalanche triggered by heavy rain. SE aspect ~6000' above Schriebers Meadow. This is a lot smaller than ones you'll probably see Tuesday. Note the runnels, which you can expect to see as well. 

    Photo: Graham Clark

Avalanche Discussion

You may see glide avalanche activity during this large rain event. Steep slopes with smooth underlying surfaces like rock slabs and low shrubs are culprits. If you see cracks in the snowpack, avoid traveling beneath those areas. They could exist at all elevations, including the shallow lower-elevation snowpack.  

Two to three feet of snow was present above about 4000 feet before the current weather event began Thursday 11/30. That snow was a mix of crusts, wind-packed snow, and weak facets on northerly aspects. Since then, 3 or more feet of snow has likely fallen at upper elevations. The storm started cold, with snow down to about 500ft. Temperatures have consistently warmed and will peak Monday night when the highest precipitation rates pass through with this atmospheric river. As of Monday evening, we've totaled about 4.5" of water at the Heather Meadows weather station. We're forecasted to double that amount by the end of the day Tuesday. Most avalanches will probably occur at the new snow/old snow interface, possibly in the old snow layer or even at the ground. 

Much of the snowpack is saturated and unsupportable so travel will be a challenge no matter your method of transport. It's early season and especially with an unsupportable snowpack you'll have an easier time hitting obstacles hidden by the snow. Creeks will be flooded. Keep this in mind if you plan to head out.

Regioni coperte