Avalanche forecast

East Slopes Central

Northwest Avalanche Center
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Avalanche danger

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

The snowpack remains sketchy out there despite the break in weather. You can still trigger a large, unsurvivable avalanche that breaks 2-4 ft deep on weak snow above a crust. Continue to avoid being on and under large, open slopes greater than 30 degrees. 

Avalanche problems

  • Persistent Slabs

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

    Weak, faceted snow over the Early February Crust created a tricky and dangerous persistent slab problem throughout much of the East Central Zone. Multiple human-triggered and natural avalanches have failed on this persistent weak layer. On Friday, a fatal avalanche accident occured in East South zone  involved this layer of facets over the Early February Crust (EFC). A preliminary report is in the discussion below. After the recent storms, a thicker slab exists over this weak layer, so avalanches will likely be much larger. A smaller avalanche could also step down to this layer. You can trigger a persistent slab avalanche from low-angle terrain below or adjacent to steep slopes, and they may propagate widely across terrain. You may or may not observe signs of instability, like collapsing, before triggering an avalanche, and it may not 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. These are not conditions where you can manage the hazard on a small feature scale, as large slopes can fracture at once, running through lower-angle benches and small features. 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. Heavy rain likely created a thick, slippery crust at lower elevations and will limit avalanche potential. 

    (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
    Likely
    Size
    1–2

    Winds will continue to move new snow into stiff, cohesive slabs on leeward features. On Saturday, observers around the zone 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 appear as rounded, pillow-like, and sometimes sound hollow. Any triggered wind slab has the potential to step down to older buried weak layer and become a much larger, unsurvivable avalanche. So continue to avoid steep wind loaded features until our weak snow has healed up.

     

    (2/16/2024)

    Visual observations help you anticipate wind loaded slopes.

    Photo: Dallas Glass

Avalanche Discussion

Preliminary Report: An avalanche accident occurred on Friday, March 1, near Darland Mt in the Ahtanum Meadows area. Two snowmobilers were involved in the slide. One rider was fully buried and killed. The avalanche occurred around 6600ft in a generally east-facing bowl. NWAC staff will visit the accident site on Saturday. Our deepest condolences to the family, friends, and community.

Over the past few days, 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. On Friday a group of snowmobilers remotely triggered a large avalanche in the north fork of the Teanaway drainage. 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. 

Observers on Dirtyface, Long Pass, and Salmon La Sac have also reported whumphing collapses on the facets above the Early February Crust (EFC). On Thursday, the Mission Ridge Pro Patrol triggered wind slabs that stepped down to the EFC and propagated widely during avalanche mitigation work.

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.

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