Avalanche forecast

East Slopes Central

Northwest Avalanche Center
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Avalanche danger

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

Despite the more favorable weather, the snowpack structure is poor, and conditions will be slow to improve. You could still trigger avalanches on deeply buried weak layers. These slides are likely to break widely across terrain, and they can be triggered from a distance and catch you off guard from above. Avoid traveling on or directly under steep open terrain.

Avalanche problems

  • Persistent Slabs

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

    This unfortunate persistent slab problem may plague our forecast and force our terrain selection to low-angle slopes for a while. Weak, faceted snow over the Early February Crust (EFC) is the weak layer responsible for numerous close calls throughout all of the eastern Cascades and a fatal avalanche accident near Darland Mountain on Friday.  These avalanches are failing 2-4ft deep, propagating widely, and being remotely triggered from low-angle terrain below or adjacent to steep slopes. A smaller avalanche could also step down to this layer. This tricky problem can give inconsistent signs of instability. You may not see any apparent signs of instability before the whole slope fails, and it may not even be the first person on the slope to trigger it. 

    Avoid traveling on or under slopes over 30 degrees. Give steep open slopes wide safety margins. Stay off of and out from underneath steep slopes at elevations above approximately 4500ft, where 1-3ft of new snow has accumulated since 2/24. Little snow exists over this crust at lower elevations, limiting the potential for avalanches.

    (3/2/2024)

    You can trigger large avalanches like this on Sunday. This avalanche would easily be large enough to bury or kill you. 

    6600 ft, NE aspect in the East- South zone.

    Photo: Katie Warren

  • Wind Slabs

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

    Continued winds will drift the new low density snow into stiff, cohesive slabs on leeward features. On Saturday, observers in Ahtanum Meadows reported gusty winds and plumes along ridgetops. You'll typically find these wind slabs downwind side of ridges, below cornices, and under rock and cliff bands. Use visual clues such as blowing snow, sharp cornices, and textured surfaces to help you identify wind-loaded slopes. These slabs will often look rounded, pillow-like, and sometimes sound hollow.

    A wind slab has the potential to step down to older buried weak layer and become a much larger, unsurvivable avalanche. With these complex and overlapping problems, use a conservative mindset and avoid steep wind-loaded terrain. 

    (2/2/2023)

    Example: Very small windslab beneath a cornice. East at 6,600ft in the upper Icicle.

    Photo: Katie Warren

Avalanche Discussion

Some moderate winds and light snow are possible tomorrow. But there is a chance for sunshine, and if it stays around for a while in the afternoon, you may see some small, wet loose avalanches, rollerballs, and pinwheels. 

Over the past week, forecasters and observers throughout the Wenatchee Mountains, the Teanaway, Salmon La Sac, and near Leavenworth have all found a weak snowpack structure. Snowpack tests consistently produce results that indicate triggering a persistent slab avalanche is likely. Observers in the Icicle on Sunday saw a crown that we suspect ran on the EFC. In the Teanaway drainage on Friday, group of snowmobilers remotely triggered a large avalanche. This avalanche occurred on a ENE aspect at 6400 ft and broke 1-2’ deep ( observation here). Another large, natural avalanche near Van Epps Pass occurred earlier this week. 

Our snowpack is complicated due to the intermittent dry spells in February. There are also potential layers of surface hoar and faceted grains from the 14th, 18th, and 24th. Widely propagating avalanches could fail on any of these layers. Approach the mountains cautiously and enjoy some low-angle powder until these weak layers gain strength. But be patient, as it could be a while before we see improved snow stability. 

This pattern of persistent slab problems can be incredibly challenging for backcountry decision-making. It takes extremely conservative terrain management and patience. This winter's lower-than-average snowfall and warmer-than-average temperatures contribute to a shallow snowpack prone to developing these tricky weak layers. The issue is especially apparent in the eastern Cascades, which, on a typical year, is already a bit shallower and weaker than areas west of the crest. So, if you're venturing into these eastern zones this winter, be prepared to take a step back in your typical terrain selection and understanding of the snowpack. It's easy to be surprised in these conditions, so with the increased complexity of the snowpack, choose low-angle terrain to enjoy the fresh snow.

Thanks to everyone who submitted observations over the weekend. It really helps us track the snowpack and avalanches during these active periods. 

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