Avalanche forecast

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Northwest Avalanche Center
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Avalanche danger

Tue
Alpine
4 · High
Treeline
4 · High
Below
3 · Considerable
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Highlights

Another jump in freezing levels will maintain very dangerous conditions in the mountains. Wet avalanches running on deeply buried weak layers will be easy to trigger and are likely to run naturally. These avalanches can be extremely destructive and hard to predict. Avoid all avalanche terrain, including the runouts of large avalanche paths. 

Avalanche problems

  • Wet Slabs

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

    Make very conservative travel choices and stick to low-angle terrain in forested areas. Avoid traveling underneath large open slopes and in the runouts of avalanche paths from much higher elevations. Wet slabs and moist persistent slabs can break widely across terrain features and be 2-3ft deep. Continued warming overnight and into Monday will only make these avalanches more likely. At lower elevations and the eastern foothills, we'll likely continue to see wet loose avalanches and maybe smaller wet slabs that run on or near the ground. Wet slab avalanches can be very difficult to predict, and the peak instability often lags behind the peak precipitation. The precipitation is tapering off, but freezing levels will soar to over 10,000ft by Monday afternoon. The weak snowpack structure has proven problematic even with minimal warming and rain. We expect the snowpack to weaken further with additional warming. There are two persistent weak layers: small facets buried on or around January 8th in the top 1/2 of the snowpack and a series of crusts and large weak grains from December in the lower 1/3rd of the snowpack. An intense storm reactivated these layers on January 17th and a warm-up on the 20th. Observers reported cornice-triggered, human-triggered, and natural avalanches on the 25th, 26th, and 27th, respectively.

    (1/25/2024)

    A recent natural avalanche (D1.5) likely ran on an older weak layer and may have been initiated by cornice fall. Poster/Pika Pk NE, 7,2000ft

    Photo: North Cascades Mountain Guides

  • Cornices

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

    Cornice Falls will become even more likely as temperatures continue to warm. Use extra caution near cornices while traveling on ridges, and make sure to give them plenty of space. There were multiple reports of recent cornice falls during the last warm-up, including some that triggered deep avalanches. Consider that a natural or triggered cornice fall could be enough to gouge into deeper layers, resulting in a very dangerous slide.

    (3/10/2022)

    An example of a very large cornice triggered avalanche.

    Photo: Matt Primomo

Avalanche Discussion

We don't have many observations from Sunday in East North zone, but temperatures jumped above freezing, and 0.5" of water was recorded at the Washington Pass weather station. Higher elevations warmed faster, so there is potential for a freezing rain crust in some areas at mid and lower elevations. A bit further south in East Central, avalanche professionals observed very large (D3) natural wet avalanches near Holden. In other areas with a weak snowpack structure, the slow warming delayed the peak of natural avalanche activity. On Saturday, Stevens Pass and Mission Ridge had skier-triggered D2.5 avalanches that ran on weak snow over buried crusts. While East North has received less water overall, the continued warming and this tricky avalanche problem mean the best plan, for now, is just to avoid all avalanche terrain. 

On Saturday, observers on Kangaroo Ridge reported a large collapse on the January 8th facets and audible natural avalanches in nearby terrain. On Friday, observers remotely triggered a very large persistent slab avalanche on an east aspect at 6,000ft in Leap Creek. Riders also triggered a small wind slab avalanche in Liberty Bowl near Blue Lake. An NWAC forecaster near Varden Creek (NNE, 5,400ft) found propagating test results on the early January facets in the middle of a shallow snowpack (65cm with HS 117cm). On Thursday, a recent natural avalanche was reported from the Hairpin Valley on Poster/Pika Peak, NE, 7,200ft. Observers believe the avalanche may have been initiated by a cornice fall and ran on the early January weak layer in the top 1/3 of the snowpack (50cm below the surface with HS 150cm).

On the 24th, NWAC forecasters traveled near Blue Lake. At a profile site (NW, 6,650ft), they found propagating test results on the January 8th facets ↓65cm and sudden collapse failures on old facets and crusts from December. The structure of older, stiff slabs over the thin, weak layer of January 8th facets, ~2 feet below the surface, matches a profile near the Poster Peak avalanche. On the 23rd, a forecaster reported a number of small, loose dry and wet avalanches in very steep, craggy terrain. Warming temperatures moistened snow surfaces up to about 6,000ft on all aspects. 

Other recent observations pertinent to persistent slabs are:  

  • Another large cornice-triggered avalanche in Cutthroat drainage ran on a deeper weak layer, likely occurring on the 21st. Deeper crowns were spotted since the January 16th storm, though visibility was poor.
  • On the 21st, an observer in the Twisp River area found that the mid-December crust produced unstable propagation saw test results. They also experienced loud whumphs that shook trees as the collapse propagated widely across the terrain.
  • Observers reported a couple of older D2.5 avalanches that ran on deeper weak layers near Hart's Pass, likely around the storm of January 17th. These occurred on an east aspect at 7,000ft and a west aspect at 5,800ft.

If you're in the mountains, please let us know what you find.

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