Bollettino valanghe

Stevens Pass

Northwest Avalanche Center
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Pericolo valanghe

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

Plan to take a big step back with your terrain selection on Thursday, as over a foot of new snow is expected to create storm slabs that are easily triggered. Most avalanches occur during, or directly after a heavy snowfall event and Thursday is one of those days. Choose lower angled terrain, and look for signs of instability such as shooting cracks and fresh avalanches.

Problemi valanghivi

  • Storm Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Likely
    Dimensione
    1–2

    Over a foot of new snow is expected to fall in a short amount of time. The storm snow is not expected to bond well with the existing weak snow surfaces. With this in mind, you could trigger avalanches from a distance, or even from below. Avalanches may be larger and more easily triggered at higher elevations, where the wind creates thicker slabs. Even below treeline and outside of the wind, enough snow may fall that you could initiate soft slab avalanches on convex rolls and unsupported steep slopes. 

    Look for shooting cracks and check to see how the new snow is bonding through a number of tests like skin track pie wedge tests, hand shears, and test slopes. If you find signs of instability or around 12" or more of new snow, stay off of steep slopes. Loose dry avalanches may run naturally during times of heavy snowfall. Stay out from underneath very steep slopes if it's snowing hard.

    A small, shallow soft slab avalanche.

    Photo: Irene Henninger

Avalanche Discussion

Thursday brings a solid round of new snow following a stretch of mostly clear, and very cold weather. This weather has created a variety of weak snow surfaces, with diurnal near-surface facets and large surface hoar on shaded slopes, to radiation recrystallization on steep south slopes. We expect the snow surfaces that get covered up Wednesday night to become a weak layer for avalanches for a few days, if not longer. Expect another cold day, along with heavy snowfall and blustery winds. There is some potential for a Puget Sound Convergence Zone to set up by afternoon, which could deliver even more snow to the area.

Since the Solstice, storms totaled over 3 feet at the top of Stevens Pass. You may find a thin crust from the Solstice on mid to higher elevation slopes. Recently an observer noted some weakening of the bonds associated with this interface due to the very cold temperatures. Observers reported natural avalanches that likely ran between the 25-26th including a notable  (D3) avalanche that broke widely across alpine terrain on a NE aspect of Mt Mastiff (see photo below). 

Stay away from tree wells and keep your partners within sight and voice contact.

Regioni coperte