Avalanche forecast

West Slopes Central

Northwest Avalanche Center
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Avalanche danger

Wed
Alpine
4 · High
Treeline
4 · High
Below
3 · Considerable
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Highlights

Strong winds, continued snowfall, and cooling temperatures will maintain very dangerous avalanche conditions at upper elevations. Very large natural avalanches could run full track to valley bottom. Avoid exposure to avalanche terrain Tuesday.

Avalanche problems

  • Storm Slabs

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

    The Mountain Loop area received several feet of snow since Friday, and an additional 1-2ft of new snow is expected by Tuesday afternoon with snow levels dropping to 1000ft. Recent storm snow needs time to settle and stabilize, and incoming snow will thicken existing slabs and build new ones. Strong south and west winds will continue over the next 24 hours, blowing snow and loading leeward slopes. The most dangerous conditions will exist in upper elevation terrain where the potential for very large natural avalanches continues. Cornices will continue to grow and could drop onto slopes below acting as huge triggers. Avoid all avalanche terrain as the snowpack adjusts to this heavy loading event.

    (2/22/2021) Natural avalanches on Shuksan Arm breaking 2-3ft+ deep and hundreds of feet wide. Photo: Ben Williamson

  • Deep Persistent Slabs

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

    Ongoing snowfall and wind will continue to test deep weak layers in the snowpack. Observations are limited in the West Central, and high uncertainty exists regarding the mid-January persistent weak layer in this zone. The deep slab problem appears to be waking up in the adjacent Stevens Pass Zone with reports of several very large natural avalanches, and one confirmed avalanche on the mid-January persistent weak layer in the Skyline area. Similar conditions may exist in the Mountain Loop area. Avalanches could run into valley bottoms and break mature timber becoming very destructive. Give this scary problem a wide berth and continue to stay off of, and well out from underneath avalanche terrain and runout zones. 

    (2/20/2021) This deep avalanche likely failed on the mid-Jan crust Saturday in the Stevens Pass Zone (S, 4900ft). Photo: Wash DOT NCR.

Avalanche Discussion

A widespread natural avalanche cycle occurred Sunday night and Monday with numerous D3+ avalanches reported throughout the Stevens Pass, Snoqualmie, and West North Zones. Continued natural activity was reported by avalanche workers along the Hwy 2 corridor through Monday evening.  A very large natural avalanche hit Hwy 20 outside of Newhalem near Gorge Dam (see photos below). The avalanche ran on the south face of Davis Peak, one of many slide paths the WSDOT avalanche program monitors (WSDOT Avalanche Atlas, Avalanche Path Atlas Photo). Historically, this path runs at least once per winter. The avalanche likely ran for more than 4000 vertical feet, and debris flowed over mostly exposed ground with little snow cover for ~1800ft before hitting the road. Avalanches on Shuksan Arm were also impressive, breaking 2-3ft+ deep and propagating hundreds of feet wide. 

The atmospheric river event isn't letting up quite yet for the West Central Zone, and the next 24 hours will bring cooling temperatures and heavy snowfall. Strong westerly winds are forecast Monday night and Tuesday, and significant wind-loading is expected. The amount of recent and wind-blown snow is concerning enough, and the mid-January persistent weak layer may have been a player in recent avalanche activity. Tuesday will be a good day to wait out the storm and let mother nature run its course. If you do venture out, be certain of your ability to identify and avoid avalanche terrain. 

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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