Lawinenlagebericht

West Slopes Central

Northwest Avalanche Center
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Lawinengefahr

Wed
Hochgebirge
3 · Erheblich
Waldgrenze
2 · Mässig
Unterhalb
2 · Mässig
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Kernpunkte

Dangerous avalanche conditions linger at upper elevations. Very large avalanches occurred recently in adjacent zones, and a deeply buried persistent weak layer continues to plague the snowpack throughout many parts of the region. Choose conservative terrain, and avoid wind-loaded alpine slopes greater than 35 degrees. 

Lawinenprobleme

  • Wind Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    1–2

    Recent storm snow may still be reactive to human traffic on slopes greater than 35 degrees, especially in wind-loaded areas. Avalanches could be 6in to several feet thick. Pay attention as you transition into wind-affected terrain looking for textured snow surfaces and firm and hollow snow. Cornices will also require extra caution. These unpredictable features could fail, acting as huge triggers on slopes below. On solar aspects, a melt-freeze crust buried February 25 may still be a good sliding surface for avalanches. On the aprons of steeper slopes or areas below gullies and cliffs, buried graupel was reported recently as well. With all the variability, be sure to evaluate the upper snowpack carefully. Use visual clues to identify and avoid large wind-loaded features at upper elevations. Recent avalanches, shooting cracks, and collapses should direct you to lower angled terrain. 

    This small slab avalanche failed naturally, probably on Friday, in the West North zone. D1, 1ft failure depth, north facing. The tracks are from 2/27. Photo: Adam U

  • Deep Persistent Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Unlikely
    Größe
    3

    A persistent weak layer involving facets on or within a crust that was buried in mid-January has created a lingering instability throughout the Cascades for over a month. Observations in the West Central Zone are limited, but very large deep slab avalanches were reported recently in the Stevens Pass, Snoqualmie Pass, West South, and East Central zones, while to the north, the mid-January persistent weak layer is not believed to be the culprit in the vast majority of recent avalanche activity. Even though human-triggered avalanches on this layer may be unlikely in the West Central, the uncertainty and unpredictability of deep persistent slab avalanches should determine where and how you travel. Continue to avoid large, steep, open slopes at upper elevations.

    (3/1/2021) A very wide, very deep avalanche released from the east bowl of Chair Peak at some point between Sunday night and Monday morning (NE-E-SE 5800; HS-N-D3.5/R4-O). Photo: Bryce Hill

Avalanche Discussion

Conditions vary throughout the West Central Zone. Several very large avalanches occurred during the avalanche cycles on February 22 and 25, and others occurred in the last few days (observation), possibly on the deep persistent weak layer. Make sure to do your homework and carefully investigate the snowpack. Give cornices a wide berth, especially during conditions like this. Tuesday looks to be a quieter day weather-wise with a slight cooling trend. Despite any significant weather inputs, stay observant, and keep your eyes peeled for signs of instability. 

Several adjacent zones are in a prolonged period of unstable conditions with continued natural and human-triggered avalanches. The deep slab problem continues to pose high consequences and demands a conservative approach to terrain and travel choices. WSDOT closed Highway 2 for avalanche control for a portion of the day Monday but were able to reopen the road by early afternoon. With explosive triggers, one D3 avalanche on the deep persistent weak layer occurred, along with several D2 avalanches in recent storm and wind drifted snow as well as wet loose avalanches. In the East Central Zone, a natural D3.5 avalanche occurred in upper elevation north facing terrain and is suspected to have run in the past 24 hours. At Snoqualmie Pass, very large natural avalanches ran in the past 24 hours including an impressive D3.5 avalanche on Chair Peak (photos below).

During the ongoing Covid-19 pandemic, continue to follow the latest guidance from local, state, and federal health officials. Avoid unnecessary risks that could impact first responders and stress medical resources.  Wear a mask when appropriate, practice social distancing, and consider recreating closer to home.

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