Avalanche forecast

Snoqualmie Pass

Northwest Avalanche Center
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Avalanche danger

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

A significant winter storm will create dangerous avalanche conditions at the Pass by Saturday morning. Be suspicious of any open slope over 35 degrees, especially at mid and upper elevations. Some avalanches could trigger easily and run quickly on a firm crust below.

Avalanche problems

  • Storm Slabs

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

    Stormy weather with high precipitation rates, strong winds, fluctuating temperatures, and significant snowfall all point towards unstable storm slabs. This is a day to dial it back and simply avoid steep open slopes. You can look for and test these storm slabs by using hand pits and small slopes to see how the new snow reacts and if it's bonded to the old surface When you see it crack, fail suddenly, or slide in blocks, you’ve found the problem. At mid and upper elevations, the new snow may not stick well to an underlying firm crust. In these places, we think avalanches could fail easily and run fast. 

    While we expect avalanches on any open slope, they could be larger and harder to manage in wind-loaded terrain. Firm thick slabs may exist along the lee side of ridges and near the base of cliffs. Unless it’s scoured to a crust, be particularly careful in wind-affected areas where these bigger avalanches could occur.

Avalanche Discussion

While not a huge event, this is a significant winter storm and a big change in the weather from the past several days. With the bulk of the precipitation and strongest winds Friday night, we expect the danger to already be in place first thing Saturday morning. You may find that the hazard spikes again during periods of intense precipitation and/or blowing snow. With convective snow showers in the forecast, this could occur nearly anywhere in the zone at any point during the day. One way to manage this uncertainty is to choose routes that allow you to easily return to the trailhead without needing to travel through complex or high-consequence areas.

We’re primarily concerned with avalanches failing at or above the new/old interface (3/31). In many places, this layer is marked by a new crust (and possibly tree debris). However, prior to this storm, a variety of surfaces were observed: scoured slopes, icy crust, wet punchy snow, and pockets of dry powder. That means the new snow may react differently in various areas. Make sure to keep making observations as you travel and don’t rely on just a few data points. 

The skies should remain cloudy Saturday, but it’s April, and we can’t rule out a few sun breaks. If you start to notice the sun, odds are, so is the snowpack. You may see natural loose wet avalanches, especially near sunny rocky terrain. Some of these smaller slides could trigger slab avalanches on the slopes below.

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