Avalanche forecast

East Slopes Central

Northwest Avalanche Center
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Avalanche danger

Sat
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
2 · Moderate
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Highlights

Soaring freezing levels and sunshine usher rapid change to a cold and layered snowpack, increasing the threat natural and human-triggered avalanches large enough to kill you. Overlapping wet and persistent problems combined with a heap of uncertainty. Avoid travel on or below consequential terrain steeper than 30 degrees.

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    2–3

    Will the warming wake up these persistent slabs or will they start to gain strength? Unfortunately, rapid warming events often create awakening before the healing process occurs and these weak layers have been active recently. Given the uncertainty, it's simply best to avoid exposure to large open slopes, including those above you at this time.

    In the past two weeks, there have been six close calls and one fatality involving a layer of weak-faceted snow over a stout crust buried in early February. The most recent was on Saturday, March 9th, near Longs Pass, where a skier triggered a very large avalanche and was caught and carried but only partially buried and uninjured.  Additional snowfall has buried this layer deeper, and therefore it might be harder to trigger. But the avalanche will also be bigger if you do manage to find one.

    In many of these avalanches, the same terrain had been previously skied/ridden once or multiple times before the avalanche occurred. So it might not be the first person on the slope that triggers the slide. While this reactivity is unusual for Washington, it is typical for this avalanche problem. This problem requires patience, conservative terrain selection, and maintaining wide margins between you and steep overhead terrain.

    Avalanches that release in layers of faceted snow may propagate widely across entire bowls and ridgelines. You can trigger them from the middle of the slope or even from below. You are most likely to trigger one of these avalanches at mid and upper elevations, particularly in leeward terrain with deeper, wind-drifted snow. At some point, we expect this problem to transition to wet slab and this transition would most likely occur first on southerly aspects.

     

    (3/9/2024)

    A very large persistent slab avalanche triggered by a skier near Long Pass. They were the second skier on the slope when the avalanche occurred. The skier was caught, carried, and partially buried but uninjured. 

    W aspect, 6400ft, crown depth 2-3ftHS-ASu-R3-D3-O

  • Loose Wet

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–2

    As the sun and warmth increase further, expect the risk of wet loose avalanches to extend onto all but the most shaded aspects. Dry snow often doesn’t play nice with sun and temperature-induced warming and it exists just below surface crusts. Once the crusts break down, you'll find moist sticky snow that provides fertile ground for wet loose entrainment.  Cool easterly winds may not be enough to keep the wet avalanche activity in check. You need to evaluate the conditions where you travel and adjust your plan as necessary.

    Wet, sticky snow is a key observation that slopes around you are becoming unstable. Wet loose avalanches can sometimes pull out a slab lower on the slope.

    Example: Signs of moist snow capable of producing wet loose avalanches. Each turn produced lots of rollerballs and pinwheels in the wet surface snow. 

    Photo: Katie Warren

Avalanche Discussion

The Cascades are heading into a stretch of very warm sunny weather. It will be the first big, spring-like warming event of the year, with high temperatures in the 50’s and freezing levels over 10,000’. Very warm conditions through the weekend could produce significant slab and loose snow avalanches.  As with any warming event, there is a high level of uncertainty as to where, when, or even if this scale of avalanche activity will occur. Big natural avalanches aren’t really the kinds of things that should be taken lightly. It’s worth noting that smaller wet loose or wind slab avalanches, cornice falls, or snow shedding from cliffs can provide the trigger needed to pull out a very large avalanche. When planning for the weekend, consider that this is one of the times when an ‘improbable’ avalanche might actually occur.

The pattern of persistent slab problems can be challenging for backcountry decision-making. It takes conservative terrain management and diligent patience and as this heat wave progresses, you may decide the costs outweigh the benefits of engaging with avalanche terrain. Stepping into steep terrain at mid and upper elevations is simply just a game of chance; you may get away with it, or you could trigger a very large avalanche that is likely to injure or kill you. The structure is especially apparent in the eastern Cascades, where the snowpack is generally more shallow than at the crest. So, if you're venturing into these eastern zones, be prepared to take a step back in your typical terrain selection and understanding of the snowpack.

Since Saturday, March 9th, weather stations in East Central have picked up between 0.5” and 1.5” of precipitation. Strong winds have redistributed new snow onto leeward aspects with signs of transport observed in neighboring zones of Stevens and Snoqualmie Pass. Some areas already saw some sun and the first round of wet avalanche activity on Tuesday.  

The first big, spring-like warming event of the year, with high temperatures in the 50’s and freezing levels over 11,000’. Very warm conditions through the weekend could produce produce an extended cycle of slab and loose snow avalanches.

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