Lawinenlagebericht

Stevens Pass

Northwest Avalanche Center
Auf der Karte ansehen

Lawinengefahr

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

Very large natural and triggered avalanches occurred recently, and a deeply buried persistent weak layer continues to plague the snowpack. Conservative terrain choices are essential. Avoid going on, or underneath steep, wind-loaded slopes while the snowpack takes additional time to adjust.

Lawinenprobleme

  • Deep Persistent Slabs

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

    A persistent weak layer involving 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 potential start zones above you. Cornices will also require extra caution. These unpredictable features could fail, acting as huge triggers on slopes below. 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 let the recent snow settle, and 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.

  • Wind Slabs

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

    Wind slabs may still be reactive to human traffic on Tuesday. Even outside of wind-affected areas, triggering an avalanche in the recent storm snow is possible. A buried sun crust from last week was responsible for a skier-triggered avalanche and near miss. If you trigger an avalanche in the upper foot or two of snow, it could be large or even step down to become a very deep and destructive avalanche. With wind slabs, storm slabs, and the potential for deep slab avalanches, you should avoid large avalanche paths, especially at mid and upper elevations. Avoid wind-loaded, leeward slopes 35 degrees and steeper.  Below treeline, stick to wind-sheltered slopes and well-supported features. 

    (2/26/2021) This avalanche was about 20in deep x 200ft wide, and ran on the sun crust from February 24th. It caught a skier who was then partially buried and lost some ski gear. Southeast aspect at 5150ft in the Polaris Boundary Glade.

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. 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. 

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 Chiwaukums, a natural D3.5 avalanche occurred in upper elevation north facing terrain and is suspected to have run in the past 24 hours. 

A massive avalanche (D4) ran naturally out of a path on Rock Mountain called West Camp on Friday night. The powder cloud took out power lines and dusted Highway 2. This avalanche started on southeast to southwest aspects at around 6200ft and took out a substantial amount of forested trim line around the runout zone (see photos below). 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. Stevens Pass Ski Patrol inspected this avalanche on Saturday and found that it ran on preserved stellar crystals over the sun crust from 2/25, and snowpack tests continued to indicate the potential to create avalanches. 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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