Bollettino valanghe

East Slopes Central

Northwest Avalanche Center
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Pericolo valanghe

Thu
Alta quota
3 · Marcato
Limite del bosco
3 · Marcato
Sotto il limite
3 · Marcato
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In sintesi

Dangerous conditions remain after several feet of snow fell with strong wind in the past 5 days.  You could trigger large to very large avalanches including unsurvivable persistent slab avalanches from far away. Stay off of and out from underneath large open slopes steeper than 30 degrees.

Problemi valanghivi

  • Wind Slabs

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

    Avoid leeward slopes steeper than 30 degrees near and above treeline. Any avalanche in the new snow could step down to deeper weaker layers and result in a very large and deadly avalanche (see below). On Wednesday, you'll need to avoid both wind slabs and deadly persistent slab avalanches.

    Expect wind slab avalanches on leeward sides of ridges and on cross-loaded terrain features and even in some open terrain at lower elevations. Avalanches will be bigger and more likely at higher elevations. Pay attention to signs of wind transported snow and recent drifting as the day goes on and as you climb onto higher slopes. Take note of which aspects are drifted and notice how that changes as you move through the terrain.  Blowing snow, stiff, firm snow surfaces, and cracks shooting through the snow are all signs that you could trigger a slide.

    At lower elevations, the sun could trigger point releases on steep, solar aspects. You could trigger storm slab avalanches and loose sluffs large enough to bury you in wind-sheltered terrain. Steer around convex rollovers and unsupported slopes. You may find a few storm interfaces that could be problem weak layers including stiffer, recent snow resting over softer snow. 

    (2/11/2021) Long shooting cracks were observed in freshly drifted snow in wind exposed terrain at Stevens pass on Thursday.

  • Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Likely
    Dimensione
    2–3

    The new snow and wind stressed weak layers that are both shallow and more deeply buried. Avalanches can propagate widely, and wrap across terrain features. Recent avalanches are bullseye information indicating that it's dangerous.  Stay well out from under any large open slopes steeper than 30 degrees, as they can be triggered from a distance or from below. Make sure that you are traveling and stopping in places that are far from avalanche terrain. 

    Over the weekend, observers reported natural and triggered avalanches on a layer of facets and surface hoar in the top 1-2 feet of the snowpack. near the Cascade Crest, you may also be able to trigger avalanches about 5ft deep on weak snow surrounding a crust from mid-January. In the eastern mountains, the mid-January layer may only be 1-2 feet deep. This layer is already responsible for a number of burials and one fatality. You can use snowpack test to identify this weak layer and you may be able to feel it with a pole handle or probe. Avalanches running in recent snow could step down into the mid-January facets. 

    (2/9/2021) Persistent slab avalanches that may have run naturally on an east aspect at around 4900ft in the Knox Creek drainage above Cle Elum Lake. These are suspected to have run on the mid-January crust later in the storm cycle of Feb 5-9th.

Avalanche Discussion

Near the Cascade Crest, over 3 feet of snow has fallen since the 11th. You may find slightly stiffer snow near the surface resting on softer, lower-density snow that fell over the weekend. The recent snow is covering weak surfaces in the form of near-surface facets, surface hoar, and sun crust. Over the past 10 days there have been many very large avalanches, avalanche involvements, and signs of instability including the following: 

Tuesday: ObserverWSDOT forecasters on neighboring Stevens Pass triggered multiple large and a couple of very large avalanches during control work early Tuesday AM.

Monday: Mission Ridge Ski Patrol triggered avalanches with control work on leeward wind-loaded slopes above treeline. Some were big enough to bury a person. They reported cracks shooting through the snow up to 15 feet. An observer just out of the ski area boundary also reported a small natural wind slab avalanche and shooting cracks. In the Icicle drainage, observers remotely triggered 

Sunday and Saturday: Observers reported natural and triggered avalanches with 1 foot of recent snow and significant wind drifting. Others noted a large whumph on a north aspect at 5,600ft at Blewett pass, and shooting cracks where the 10" of wind thickened new snow sat over weak faceted grains below treeline. Observers in the Icicle drainage remotely triggered a large avalanche (about 1.5 feet deep)  from about 150ft away on a S aspect at 6100ft. They also got a large collapse on the mid-January weak layer at 4,900ft on an ESE aspect.

February 8th: Two snow bike riders were caught and buried by a very large avalanche in the mountains west of Salmon la Sac Sno-Park along Cle Elum Lake (See the short video in the media gallery below). One snow biker was partially buried and was able to dig himself out. The other rider was fully buried and killed. The avalanche (HS-AV-R3-D3-O) occurred on a northeast aspect at 4400 ft in the Knox Creek drainage. Our deepest condolences to the family, friends and community.

February 6: a D3 avalanche resulted in a full burial with no injuries near the Easton Sno-Park. Numerous other reports of wide and deep avalanche activity came in from the 6th-8th, including one on an east aspect of Sixtysix Hundred Ridge in the Icicle drainage that was roughly 1500ft wide and ~3ft deep. 

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