Bollettino valanghe

Stevens Pass

Northwest Avalanche Center
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Pericolo valanghe

Thu
Alta quota
3 · Marcato
Limite del bosco
3 · Marcato
Sotto il limite
2 · Moderato
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Non aggiornato — questo bollettino è scaduto 6 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

Dangerous conditions continue after significant snowfall and wind stressed weak layers of snow this weekend.  Stay well out from under wind-loaded, open terrain 35 degrees and steeper. Consider avoiding avalanche terrain at upper elevations where you can trigger very large and destructive avalanches that could break widely across slopes.

Problemi valanghivi

  • Wind Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Likely
    Dimensione
    2

    Watch for wind-stiffened snow and recent drifts. Avoid leeward and cross-loaded slopes where westerly wind has deposited slabs over the past week. Avalanches will be bigger and easier to trigger above treeline. Any slide could break into older weak layers of snow causing a very large and destructive deep persistent slab avalanche. Use caution near cornices and the edge of ridgelines. You can use small, inconsequential slopes to check if the storm snow slides or cracks easily. In wind-sheltered terrain, you could trigger small loose dry avalanches on slopes near 40 degrees.

    (2/8/2021) Cornices and wind drifting on Mt. Snoqualmie in the neighboring Snoqualmie Pass zone on Monday.

  • Deep Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    3

    Deep persistent slab avalanches are difficult to manage and can catch even experienced travelers by surprise. The best way to stay safe is to avoid large, open slopes 35 degrees and steeper especially at upper elevations where wind loading has occurred. Put a large buffer of terrain between where you travel and large avalanche paths. Make sure to regroup and stop only in truly safe terrain, well away from and out from under steeper slopes. While these avalanches may be less likely below treeline, there's uncertainty and the snowpack structure can be found in open terrain above 4,000ft. These avalanches give little warning before releasing. When in doubt, avoid avalanche terrain.

     A widespread cycle of slab avalanches ran on persistent weak layers from Friday through Sunday. Observers confirmed avalanches that broke widely and were remotely triggered on this layer, including an avalanche burial, resulting in no injuries on Jim Hill. About 3-4 feet below the surface, you can find a softer layer of weak faceted snow above or around a crust that formed in mid-January. Sudden and propagating snowpack tests on this layer can indicate the potential for an avalanche.

    (2/7/2021) Skiers triggered a very large (D3) avalanche which partially buried 2 people on February 7th. The avalanche released on a NE aspect at 6,100ft on Jim Hill in the Stevens Pass zone.

Avalanche Discussion

An avalanche fatality occurred on February 8th in the Knox Creek drainage in the neighboring East Central zone. Our condolences go to the friends and families of those involved. Similar avalanche conditions exist in this zone.

The past week brought significant snow, wind, and avalanches. The peak of natural avalanche activity at Stevens Pass likely occurred Saturday night into Sunday but reports of natural and human-triggered slides continue to come in. Two backcountry skiers were partially buried but fortunately not injured in a very large avalanche on Jim Hill on Sunday. The most recent known avalanche occurred on Monday on a SE aspect of Highlands Bowl (photo below). This slope was also the site of a widely propagating avalanche on Friday and skier triggered avalanches on January 27th.  A very large natural D3 avalanche likely ran on the night of the 6th on a NW aspect of Jim Hill into the Lanham Creek drainage. There were also reports of very large natural avalanches on a SE aspect, 5,400ft in upper Nason Creek, a SW aspect, 5,800ft in Tunnel Creek (photo below), and NE slopes 5400-5500ft above Lake Susan Jane and Swimming Deer Lake.  After avalanche mitigation on Sunday, Stevens Pass Patrol reported triggering widespread and touchy loose dry and soft slab avalanches in the recent snow along with a few slopes still breaking 3-4 feet deep to the mid-January crust.

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.

Regioni coperte