Lawinenlagebericht

Stevens Pass

Northwest Avalanche Center
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Lawinengefahr

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

The potential for deep and destructive avalanches lingers and demands conservative terrain choices. Strong solar radiation and warming temperatures will raise concern for wet avalanches and cornice fall. Continue to avoid travel on or below large open slopes, especially at upper elevations.  

Lawinenprobleme

  • Deep Persistent Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    3–4

    A persistent weak layer of facets on or within a crust that was buried in mid-January has created a lingering instability for over a month. The uncertainty and unpredictability of deep persistent slab avalanches should determine where and how you travel. Avoid going into, or underneath open or sparsely treed terrain with large start zones above you. Slopes 5000ft and above and on east/south/west aspects are of most concern and have recently produced avalanches of D4 in size, over 1500ft wide, and up to 10 feet deep. Unfortunately, this problem isn't going away for a little while, and we shouldn't be surprised to hear about more of these monsters in the next few days. Continue to tread carefully if you venture out into the mountains.

    A deep persistent slab avalanche ran naturally at around 10:30pm on February 26th in a path known as West Camp off Rock Mountain above Highway 2 east of Stevens Pass. Southeast to Southwest aspects with the crown running from around 6200ft to 5400ft.

  • Cornices

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    2–3

    Cornices will require extra caution on Wednesday. These unpredictable features loom in many upper elevation areas and will weaken in the strong March sun. If they fail, they could act as huge triggers on slopes below and result in very large and destructive avalanches. Give cornices a wide berth while traveling along ridgelines, and avoid exposure to all cornice features above. Also, recent deposits of wind-blown snow may still need time to settle and stabilize. Continue to steer around large wind-loaded slopes greater than 35 degrees, especially at upper elevations.

    (2/28/2021) Large cornices formed during the recent storms throughout the Stevens Pass area.

  • Loose Wet

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

    Expect warming temperatures and strong solar radiation Wednesday. Watch for snow surfaces to become wet and weak throughout the day as skies clear, with the best chance for wet avalanche activity in the afternoon. You are most likely to encounter loose wet avalanches on sun-exposed slopes, but all aspects are suspect with freezing levels rising to 5000ft. Rollerballs and pinwheels are a good indicator that loose wet avalanches could follow. Steer away from terrain traps like gullies or slopes above cliffs that magnify the consequences of even a small avalanche. Keep in mind that wet loose slides in motion could even trigger slab avalanches. Move to shaded or lower angled terrain to reduce your risk. 

    (3/2/2021) Large rollerballs on a NE aspect at 4800ft in Henry Creek. Photo: Adam Butterfield

Avalanche Discussion

We 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. Another significant warm-up on Wednesday will make matters more complex and raise uncertainty. Stay observant, and keep your eyes peeled for signs of instability. 

Reports of impressive deep slab avalanches continue to trickle in, including very large naturals 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 (the remaining hangfire in West Camp path), along with several D2 soft slab and wet loose avalanches. In the Chiwaukums, a natural D3.5 avalanche occurred in upper-elevation north-facing terrain and is suspected to have run on Sunday. At Snoqualmie Pass, very large natural avalanches ran each of the past several days including an impressive D3.5 avalanche on Chair Peak. A massive avalanche (D4) ran naturally out of a path on Rock Mountain called West Camp on Friday night. A partial burial occurred on Friday just outside of the Stevens Pass Ski Area boundary. This avalanche (D2) was 18-20in deep, about 200ft wide, and ran on a steep southeast aspect at 5150ft. We are glad the person is ok. From the 20-23rd, the Schmidt Haus station picked up a whopping 6in of water equivalent. Numerous very large and destructive avalanches ran during a period of High to Extreme avalanche danger on the 21-23rd.

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