Avalanche forecast

East Slopes Central

Northwest Avalanche Center
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Avalanche danger

Mon
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
3 · Considerable
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Highlights

Unusual and dangerous conditions exist in the mountains, especially in the southwest portion of the zone such as the Salmon la Sac and Teanaway. Unsurvivable persistent slab avalanches may be triggered easily in avalanche terrain. Plentiful snow, wind, and very cold temperatures have created reactive soft slabs and wind slabs. Stay off of, and out from underneath steep open slopes where avalanches can break on any number of layers, up to 4ft deep.

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    2–3

    The new snow and wind drifting may be stressing deeply buried weak layers. You can trigger avalanches up to 4ft deep on weak snow surrounding a crust from mid-January. This tricky layer is already responsible for a number of burials and one fatality. Slabs can propagate widely, and wrap across terrain features. Stay well out from under any large open slopes steeper than 30 degrees, as they can be triggered from a distance or from below. Most likely, you won't get a warning sign of whumphing collapses, or if you do, it could turn into a deadly avalanche. You can check for this weak structure with a pole handle or probe for weak snow above a crust as you travel. Recent avalanches are the bullseye information we need, no need to dig pits for now, because we know it is dangerous. Experienced travelers have commented on how they really need to rethink their terrain choices and greatly increase their 'safe zone' margins after seeing one of these avalanches.

    The Salmon la Sac, Teanaway, Icicle, and other areas on the south and western edge of the zone have been favored for recent snowfall and wind, and therefore may be most dangerous for an avalanche on this layer. Previously, most avalanches were on Northwest to Southeast aspects, but recent sustained easterly winds may be overloading west facing slopes. 

    (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.

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–2

    Easterly winds have been blowing since Thursday, and should switch back to the west on Sunday. Slabs will grow on lee aspects, but you could find them on all aspects due to this wind shift. Look for these especially in areas near passes and east-west oriented valleys, where the wind gets funneled. Feel for slightly thicker snow, and look for signs of wind drifted snow and shooting cracks. Slabs could be surprising and triggered from a distance, as many sit over faceted grains and surface hoar. If you find any instabilities, stay off of steep slopes. Any avalanche in the new snow could step down to deeper weaker layers and result in a very large and deadly avalanche above 4,500ft. Consider the terrain you're connected to and avoid steep, open wind loaded slopes. 

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

Avalanche Discussion

Around 8" to 14" of snow has fallen since the 11th. Very cold temperatures has squeezed out this low density snow, and it has begun to add up, especially in the south and southwest parts of the zone. The new snow and freshly drifted snow is covering weak surfaces in the form of near-surface facets, surface hoar, and suncrust. This adds another problem to our already complicated snowpack, so consider avoiding avalanche terrain through the weekend. The temps are cold enough that any accident or incident holds even higher consequences, as frostbite and hypothermia are a very real hazard. 

Over the past week, there have been many very large avalanches, avalanche involvements, and signs of instability including the following: 

Saturday: Observers noted one 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.

Friday: An observer reported hearing a number of loud natural avalanches near Cooper Lake.

February 9th: Natural avalanches may have occurred near Stevens Pass and Snoqualmie pass. These were on an East aspect at 5,800ft (Stevens), and a Northeast aspects at 5,000ft (Snoqualmie, see photo below). 

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.

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