Bollettino valanghe

East Slopes Central

Northwest Avalanche Center
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Pericolo valanghe

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

You are likely to trigger wind slab avalanches below ridgelines or on lee open slopes with recently drifted snow.  Smaller avalanches may step down to deeper weaker layers resulting in large and deadly avalanches.  In central and eastern parts of the zone, it may be easier for you to trigger a persistent slab avalanche that breaks widely around terrain features.  Avoid large open slopes steeper than 30 degrees and be mindful of the terrain you're connected to at lower elevations. 

Problemi valanghivi

  • Wind Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Likely
    Dimensione
    1–2

    Don't become complacent on Thursday, we have a complicated snowpack following a significant storm cycle. 

    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).  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 easier to trigger at higher elevations.  Blowing snow, stiff, firm snow surfaces, and cracks shooting through the snow are all signs that you could trigger a slide.

    In wind-sheltered terrain and for areas near the Cascade crest, you may trigger a storm slab avalanche or loose sluff large enough to bury you.  Steer around convex rollovers and unsupported slopes.  Stick to treed terrain and slopes less than 30 degrees. 

    (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

    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 weak layers lurking after this storm cycle.  Persistent slab avalanches can propagate widely and wrap across terrain features.  Continue to stay well out from under any large open slopes steeper than 30 degrees, as they can be triggered from a distance or from below. 

    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 closer to the surface. 

    (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

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.  Those storm snow totals taper dramatically from west to east across the zone, with less than 6 inches of new snow over the same period in the Wentachees.  Strong west winds since Sunday have effectively moved snow onto lee slopes for several days.  The storm ended warmer than it started, so even if you're in wind-sheltered areas, you're likely to find slightly denser snow closer to the surface.  Underneath the recent snow,  persistent weak layers lurk in the form of facet/crust combos and buried surface hoar.  Several weak layers exist in the top 1-3' of the snowpack (see photos and videos below).  The mid-Jan facet crust combo may be 5 or more feet down closer to the Cascade crest. 

It's been an active week for avalanches: 

On Tuesday and Wednesday, WSDOT avalanche forecasters in the neighboring Stevens Pass zone triggered multiple large (both days) and a couple of very large avalanches (Tue) during early morning control work. A NWAC forecaster reported a natural large avalanche on a NE aspect of Miller Peak at 5800' near Blewett Pass that likely released Mon or Tue.   On Tuesday, avalanches about a 1' deep were remotely triggered by snowmobilers south of Cle Elum and I-90 on an east aspect of Quartz Mt.  

Whumpfing, collapsing and remotely triggered avalanches about 1' - 1.5' deep were reported over the weekend near Blewett Pass, Mission Ridge, and the Icicle drainage.   

The last known avalanches down to the mid-January crust in the East Central zone are now over a week old and include:  

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 accident report). 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 4750 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