Boletín de aludes

East Slopes South

Northwest Avalanche Center
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Peligro de aludes

Sun
Alta montaña
2 · Moderado
Límite del bosque
2 · Moderado
Bajo el límite
1 · Débil
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Desactualizado: este boletín caducó 2 years ago. Estás viendo condiciones pasadas, no el boletín vigente.

Lo esencial

Slopes where the wind has deposited snow onto them are where it's feasible to trigger both small and large avalanches, but small avalanches are more probable. Consider navigating around terrain steeper than 35 degrees where you find pillow-like drifts and cornice development, particularly on aspects and elevations that harbor a weaker snowpack. You can further reduce your risk by choosing short, planar slopes free of hazards and terrain traps.

Problemas de aludes

  • Wind Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Possible
    Tamaño
    1–2

    This week was windy, and the distribution of wind-affected snow is widespread. The sensitivity of wind slabs in this zone is more uncertain. Fresh slabs will be small but have the ability to knock you off your feet and carry you over hazards such as rocks and cliffs. There is a smaller chance of triggering an older slab large enough to bury you; you will most likely find these slabs on north and west facing aspects at upper elevations.

    Regardless of the uncertainty, you should look for signs of instability. Cornice development is the most obvious clue of previous wind transport and signals that older slabs might lurk just below. Look for fresh slabs on slopes where you see the wind blowing snow onto them. If you get big cracks shooting from your equipment, hear or feel a collapse, or see a recent slab avalanche, dial back your terrain choices to more sheltered slopes.

    Although fairly unlikely, a triggered wind slab could "step down" and become a more treacherous persistent slab avalanche where poor snowpack structure exists. Read below for more details.

    (West South zone, 2/13/2025)

    Natural avalanche activity observed on the ridge between Cement and Lakes Basin. These blocks of snow fell during a period of intense winds.

    Photo: Andy Harrington

  • Persistent Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Unlikely
    Tamaño
    1.5–2

    The likelihood of triggering a large and potentially fatal avalanche is low but not impossible. This zone doesn't have any confirmed activity or signs of instability on weak snow layers associated with the January Drought Layer (JDL) this week, but we have good confidence that poor snowpack structure still exists. Areas that have been wind-loaded - where the wind has built a larger and more cohesive slab over weak layers - will be more untrustworthy. 

    This particular persistent slab problem has been even more tricky to manage than your average uncertain persistent slab problem. You may or may not see clear signs of instability - cracking, collapsing, or recent slab avalanches - telling you to back off before it's too late. Use the clues laid out in the wind slab problem to help you identify wind-loaded slopes, understanding that even a small wind slab avalanche can "step down" and trigger a deadlier persistent slab avalanche. You can reduce your risk by choosing more simple terrain free of consequential runouts. And when in doubt, low-angle it out.

    (East Central zone, 2/14/2025)

    You can clearly see the grey-ish line of weak facets in the wall behind the failed snowpack test. These weak grains aren't hiding, they're easy to spot. 

    Photo: Dallas Glass

Avalanche Discussion

The East South zone has received small inputs of snow on most days this week, and Saturday is no exception, with another 2-3 inches in the forecast. Additionally, we saw a strong easterly wind event that loaded atypical slopes. The wind shifted back to more typical westerly directions on Friday. This has kept what one could call a "lingering" wind slab problem on the table all week. With shifty wind directions and a lack of on-the-ground data for this zone, this problem has been tough to nail down. On Friday, NWAC Forecasters traveling in the nearby East Central zone noted how variable the wind-affected snow was just within this one specific area. They found reactive wind slabs on both sides of a ridgeline. Another NWAC Forecaster traveling just over the border in the West South zone found and triggered numerous small wind slab avalanches. You may encounter locales like this where it is more likely to trigger an avalanche.

We are also closely watching how the slab associated with the persistent slab problem has been settling, bonding to the JDL, and reacting to wind loading. Numerous avalanches were triggered in wind-loaded areas in the East North zone and failed on the JDL this week. The NWAC Forecasters in the East Central zone got inconsistent snowpack test results in an area with poor snowpack structure. We are now looking at a more significant storm system rolling in later on Saturday, which could quickly bring persistent slab avalanches back to the forefront. It is not so big of a system that we feel much assuredness with that claim at this time, but it's worth putting back on the radar.

Submit an observation to help NWAC Forecasters reduce uncertainty. It can be short, simple, and even anonymous. Any information you have will help us write more accurate forecasts that will, in turn, better help guide your backcountry decision making.

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