Lawinenlagebericht

East Slopes Central

Northwest Avalanche Center
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Lawinengefahr

Wed
Hochgebirge
4 · Gross
Waldgrenze
4 · Gross
Unterhalb
3 · Erheblich
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Kernpunkte

Tuesday will be a very dangerous day in the mountains. Strong to extreme winds, heavy snowfall, and various weak layers in snowpack are a recipe for large avalanches. Avalanches could break widely and run naturally from overhead. So avoid traveling on or under steep slopes until this storm plays out.

Lawinenprobleme

  • Storm Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Very Likely
    Größe
    2–3

    Tuesday won't be a day to venture into avalanche terrain. Natural and human-triggered storm slab avalanches will be widespread. Avalanches could measure 2-4 feet deep and propagate widely across terrain features. Avoid traveling on or under slopes greater than 30 degrees, particularly at middle and upper elevations where avalanches will likely be much larger. At lower elevations with a thinner snowpack, avalanches might be smaller, but they would carry high consequences if you are dragged through terrain still riddled with rocks, stumps, creeks, and other terrain traps. Strong to extreme winds will also drift snow into thicker slabs, where you could trigger a stiff wind slab avalanche. With these high wind speeds, finding sheltered slopes that lack significant wind drifting may be challenging. If you venture out into the blizzard-like conditions for winter recreation, be sure to find sheltered, low-angle slopes not exposed to overhead hazards from steep slopes above. It will be a great day to observe red flag signs of instability, like collapses and shooting cracks, from low-angle terrain.

    (1/7/2024)

    A skier triggered and took a short ride in this avalanche that failed on buried surface hoar in the Teanaway Drainage on Sunday. 

    Photo: Rob Pollard

Avalanche Discussion

Expect blizzard-like conditions in the mountains on Tuesday with heavy precipitation, warming temperatures, and winds up to 65mph. Avalanche danger will increase rapidly on Tuesday night, and we expect natural activity to continue into the day. This storm will overload the various weak layers in the mid and upper snowpack responsible for multiple human-triggered and natural avalanches over the past few days. Until this storm passes through and we can reassess the state of the snowpack, travel in avalanche terrain is not recommended. Lower elevations hold less snow and, in many places, likely do not have the threshold for large avalanches. However, we still expect smaller avalanches at lower elevations, and these could carry serious consequences with the additional terrain traps still protruding from the thin snow cover.

Over the weekend, there were widespread observations of avalanches and other red flag signs of unstable snow, including collapsing, shooting cracks, and unstable snowpack test results. On Saturday, backcountry travelers in the Blewett Pass area had a close call with a triggered avalanche that broke 1-2 ft deep and propagated widely. This large avalanche occurred on an NE aspect at 6000 ft in a wind-loaded area and likely failed on old, faceted snow from December. Near Fortune Creek drainage, we observed a large, widely propagating avalanche on a solar aspect at 6800 ft. Two other human-triggered avalanches occurred in the Teanaway and Salmon La Sac drainages, around 6000ft, but on different aspects. Luckily, these avalanches were small, and no one was injured. But as we add a substantial load to these weak layers, avalanches will quickly become very large. 

The upper snowpack has several potential and confirmed weak layers and crusts. The surface hoar buried on 1/2 is the suspected culprit in two human-triggered avalanches. The depth of the Solstice crust varies throughout the zone but is associated with weak, faceted snow above and below the crust. This layer produced large slab avalanches during control work at Mission Ridge on December 30th, and could be the weak layer responsible for the avalanche at Blewett Pass. We can't rule out avalanches in the new storm snow stepping down to these deeper weak layers and producing very large avalanches that propagate widely. Extra caution and wide margins are warranted while this storm plays through our mountains. 

The snow cover is still shallow, especially further east in the zone and at lower elevations. These hazards may lurk just under the surface after Monday night's storm, so as you seek out sheltered, angle terrain on Wednesday, don't forget about these other hazards quite yet.

If you get out, let us know what you see by submitting a public observation!

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