Avalanche forecast

East Slopes Central

Northwest Avalanche Center
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Avalanche danger

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

A combination of rising temperatures, strong sun, new and wind-drifted snow, and a tricky snowpack means backcountry travel on steep slopes is a serious proposition. Stick to simple lower-angled terrain to reduce the risk of triggering an avalanche. Use extra caution through the weekend as the Cascades see the first big warm-up of the year.

Avalanche problems

  • Persistent Slabs

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

    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.

    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.

    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.

    (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

  • Wind Slabs

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

    A wind shift to the east will change up the pattern of recent wind loading. Expect to see dry, loose snow on northerly and easterly aspects drift onto leeward or cross-loaded slopes. Blowing and drifting snow should show you exactly which slopes are loading up. Slope cuts and other simple tests can tell you about the reactivity of fresh wind slabs. Also consider that a small wind slab could in turn trigger a larger avalanche that releases in deeper layers. Given the complexity of the snowpack in many pats of the East Central forecast zone, it might be wise to just steer around steep terrain holding freshly drifted snow. 

    (3/4/2024)

    Dense, wind-drifted snow is often just below ridgeline. 

    Photo: Joe Dellaporta

  • Loose Wet

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

    Warm, sunny weather is on the horizon, and dry snow often doesn’t play nice with sun and temperature-induced warming.  But cool easterly winds can also help keep wet avalanche activity in check. You need to evaluate the conditions where you travel and adjust your plan as necessary.

    Avoid travel on or directly under steep slopes where you see signs of instability, like rollerballs, pinwheels, or small avalanches. 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.

    (3/7/2024)

    Rollerballs on small terrain are an initial sign the snow surface is beginning to warm.

    Photo: Kaitlin Harrigan

Avalanche Discussion

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 pattern of persistent slab problems can be challenging for backcountry decision-making. It takes conservative terrain management and diligent patience. 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.

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. On the other hand, 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.

Your avalanche, snowpack, or weather observations are extremely valuable to the avalanche community. Help create a more accurate avalanche forecast by submitting your observations here. 

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