Lawinenlagebericht

East 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

A potent round of westerly winds along with new snow will maintain dangerous avalanche conditions near and above treeline.  Any avalanche breaking down to weaker older snow layers would be large and destructive.  Limit your exposure to large avalanche paths as we begin a new storm cycle. 

Lawinenprobleme

  • Wind Slabs

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

    Strong to even extreme westerly ridgeline winds will move new snow onto lee slopes Thursday night and for much of Friday.  You'll find firmer wind-affected snow near and above treeline and even on open slopes below treeline.  Shooting cracks or hollow-sounding snow are signs you could trigger an avalanche on similar nearby slopes.  Avoid open slopes steeper than 35 degrees where you find freshly drifted snow, sticking to lower angle or wind-sheltered terrain.  

    In wind-sheltered terrain and for areas near the Cascade crest, you may trigger a storm slab avalanche.  Steer around convex rollovers and very steep unsupported slopes in areas you find more than 6" of new snow. 

    Example of a skier triggered wind slab on a steep, wind exposed north aspect at 5,800ft (NTL). Windy Knob, near Blewett Pass.

  • Persistent Slabs

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

    Even if you're aren't seeing obvious signs of instability like recent avalanches, or experiencing whumfping or collapsing as you travel, we know there are several weak layers still lurking 2 - 4 feet down below the surface. You can dig down in the snow to look for a thin layer of surface hoar (2/11) in the central and eastern parts of the zone (see media gallery below) or several feet down to find the mid-January crust/facet combination that was responsible for many large to very large avalanches over a week ago.   

    While it's been becoming less likely you'll trigger a persistent slab avalanche, the stakes are still very high.  If you trigger any size avalanche in the new snow, you may awaken deeper instabilities.  Closer to the Cascade crest, persistent slab avalanches breaking beneath the recent storm snow will be very large and destructive.  For areas further east, it may be easier for you to affect these layers directly.  Either way,  continue to limit your exposure to large and consequential avalanche paths. 

    (2/9/2021) Persistent slab avalanches that may have run naturally on an east aspect at around 4900 ft 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

Wow, there's a lot of snow near the Cascade crest;  over 4 feet of snow near the Cascade crest since Saturday finally took a breather on Wednesday.  Storm totals tapered dramatically from west to east across the zone. Large to very large avalanches were triggered Monday and Tuesday by Stevens Pass WSDOT in the new storm snow.  Smaller wind slab avalanches were intentionally triggered in the Mission Ridge area during control. Observations east of Stevens Pass, the Mission Ridge area and in the Teanaways on Thursday suggest that recent storm instabilities are healing and avalanches in the recent snow are stubborn to trigger.  

A new storm started to roll in Thursday afternoon with light new snow falling during the afternoon and winds starting to move winds near and above treeline.  A sun crust that formed midweek could be found on steep southerly aspects.  Underneath the recent snow,  persistent weak layers lurk in the form of facet/crust combos and buried surface hoar.  As we enter a new storm cycle,  there haven't been reports of persistent slab avalanches since the weekend (remotely triggered in the Icicle drainage) and 10 days since human-triggered very large avalanches, which included an avalanche fatality, released down the mid-Jan facet crust combo. 

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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