Avalanche forecast

Snoqualmie Pass

Northwest Avalanche Center
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Avalanche danger

Tue
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
1 · Low
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Out of date — this forecast expired 2 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

We have a good bed surface and poorly bonded storm snow above it - a great recipe for avalanches. The slab over this crust is thicker and has been more reactive in wind-loaded terrain at upper elevations. Consider the consequences of triggering an avalanche before you commit to a slope, it will be easier to do on wind-loaded, convex, or unsupported features.

Avalanche problems

  • Wind Slabs

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

    Wind-loaded terrain, particularly at upper elevations continues to be the most likely location to trigger an avalanche. Avoid wind-loaded features such as leeward ridgelines, convexities, the base of rocks/cliffs, and gullies/confined chutes. These terrain features are all common locations for the wind to sift snow into thicker slabs. Slabs will be larger as you ascend toward wind-exposed elevations with higher storm totals. Use small slopes where you're not in danger of being caught in an avalanche to test the storm snow to see how it reacts to your weight. Use numerous quick hand pits as you travel to check the bond at the 1/10 interface. It is reportedly poor, meaning that snow could fail easily on top of the crust.

    (1/11/2025)

    This avalanche has a trifecta of common terrain features where wind slabs are often found. It's a gully, near a ridgeline, at the base of rocks.

    Spend some time thinking about terrain before you commit to a slope.

  • Loose Wet

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–1.5

    The sun is going to come out and we're on a slow warming trend. It won't be blazing hot but may be warm enough to kick off avalanche activity on sun-exposed slopes. Look for rollerballs, pinwheels, new fan-shaped avalanche debris, or even the surface snow starting to "slab up" in the sunshine. Luckily, it will be easy to manage your exposure to any of these solar-induced issues by heading toward shadier aspects and keeping aware of what's above you.

    (12/23/2024)

    Wet-loosed debris that released naturally in the sun earlier this season. Similar activity could occur in the coming days.

    Photo: Summit at Snoqualmie Pro Patrol

Avalanche Discussion

Saturday morning, a group of four backcountry tourers were involved in an avalanche accident near Kendall Peak in the Commonwealth Basin area of Snoqualmie Pass. Details are still being gathered, but the accident occurred on a SW aspect at 5600ft. All four members were caught and carried. Two were injured. The party called 911 to request assistance. Search and rescue responded to the area and brought the victims to the trailhead.

There's a poor bond between the new snow and the underlying 1/10 interface, meaning triggering could be easy in some locations, such as on unsupported slopes or wind-loaded terrain. That proved true over the weekend when multiple human-triggered avalanches were reported, many of which caught and carried individuals. As mentioned in the header of the Forecast Discussion, two unlucky travelers were injured but were able to make it to safety due to a strong support team and SAR efforts. 

On Sunday, NWAC forecasters were on Kendall Peak to look at the 1/10 interface after a few observations mentioned whumpfs or remote triggers. These words often set off alarm bells that a persistent slab problem could be on the horizon. Before the storm, near-surface facets and surface hoar were observed on top of the 1/10 crust - maybe they survived the onset of precipitation and wind? A few holes in the ground on one mountainside are by no means a conclusive study, but our current hunch is that we do not have a persistent slab problem. Hand pits, small column tests, and test slopes all produced easy failures on the 1/10 crust, but we did not get propagation in any of our large column tests. We did not find much in the way of faceted grains at this interface, although rimed particles and other junk existed.

So what do we do with this pesky 1/10 interface going forward? If our theory is correct, the warm weather should help this problem heal over the next few days, hence the drop in the forecasted danger level. That said, the bond is poor enough that you should continue to avoid big terrain, especially if the slope is unsupported, wind-loaded, or convex. You should also be suspect of areas where the slab is thicker due to wind, particularly at upper elevations near rocks or confined gullies/chutes. These areas like to harbor weak grains and gather wind-deposited snow, a double no-no. We'll keep digging and trying to get ahead of this, you keep safe out there and consider traveling more like it's considerable than moderate.

Before this storm, travel conditions were very challenging due to breakable crust, icy slopes, frozen tree bombs, and piles of avalanche debris. The new snow has helped, but many of these hazards are now only a few inches below the surface, making them more difficult to spot.

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