Lawinenlagebericht

West Slopes Central

Northwest Avalanche Center
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Lawinengefahr

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

Deep and destructive avalanches remain a possibility, especially in the south and east portions of the zone. Precipitation Thursday night through Saturday will heighten concerns for wind slabs at upper elevations and wet loose avalanches on lower elevation slopes where it rained. Approach terrain with a conservative mindset, and avoid travel on or below large open slopes steeper than 35 degrees.

Lawinenprobleme

  • Deep Persistent Slabs

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

    Neighboring zones to the south and east continue to report recent very large avalanches failing 10 or more feet deep on the mid-January persistent weak layer. Aerial photos of very large avalanches from last week's avalanche cycle show evidence that deep persistent slab avalanches failed in the West Central zone as well. The weight of just a person may not be enough to cause an avalanche on this layer, but cornice fall or smaller wind slab avalanches could add the needed weight to trigger an avalanche on this layer. Warm temperatures for the last 48 hours could make this layer more reactive, in addition to the current precipitation. Continue to dial back your terrain selection and build in a wide margin for error. Seek out simple, lower angled slopes and avoid going into, or underneath open or sparsely treed terrain with large start zones above you.

    (3/1/2021) This very large avalanche occurred on the east facing slopes near Peak 7185 south of Mt Misch. The crown line was estimated to be 10-15ft at its highest point, and 700-800ft wide. Photo: John Scurlock

  • Wind Slabs

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

    Wind slabs will develop as snowfall amounts increase and wind continues throughout the day on Friday. Avalanches will most likely remain in the new snow deposited in the last 24 hours, which could amount to 6 inches by midday.  Strong winds from the south will redistribute snow onto leeward slopes and crossload features. Feel for stiffer snow and observe signs of active wind loading to determine where wind slabs are. Cornices have grown very large in recent days, and with more snow loading them they may fail triggering very large avalanches on the slopes beneath.  Avoid wind loaded slopes steeper than 35 degrees. If you see red flags such as natural avalanches and large cracks from your movement be prepared to stay even more conservative with your travel.

    (3/3/2021) Wind loading was actively occurring on Wednesday 3/3. Photo: Zach McGill

  • Loose Wet

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

    Enough rain could fall at lower elevations that the upper portion of the snowpack will get saturated with water. Avalanches may be larger than the recent small wet loose avalanches which occurred on south facing slopes. They will occur on all aspects, and possibly larger on northerly slopes which were not affected by the sun previously. These avalanches could carry large amounts of mass, which might bury you or cause harm if they push you through trees or deeply bury you in a gully. Avoid steep slopes and their runouts where the snow is getting saturated with rain, where loose wet avalanches may occur.

    Wet loose avalanches may occur on Friday. Photo: Zach McGill

Avalanche Discussion

Several adjacent zones are in a prolonged period of unstable conditions with continued natural and human-triggered avalanches. Observations are limited, but similar conditions are suspected in the West Central, especially in the southern and eastern portions of the zone. The deep slab problem continues to pose high consequences and demands a conservative approach to terrain and travel choices. Above freezing temperatures in the last 48 hours adds more instability to the equation. 

Reports of impressive deep slab avalanches continue to trickle in, including very large natural avalanches from last week on Benchmark and Fortune Mountains just north of Stevens Pass in the West Central Zone.  On Monday, WSDOT avalanche teams triggered an 8ft deep D3 avalanche on the southeast face of Rock Mountain east of Stevens Pass, along with several D2 soft slab and wet loose avalanches. On Sunday, a natural D3.5 occurred in upper elevation north-facing terrain in the Chiwaukum Range on the eastern edge of the Stevens Pass zone, as well as another D3.5 natural on Chair Peak (Source Lake) in the Snoqualmie Pass zone. See photos below for several of these large avalanches.

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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