Avalanche forecast

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Northwest Avalanche Center
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Avalanche danger

Wed
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
1 · Low
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Highlights

Winds may create shallow slabs in alpine terrain. Steer around freshly wind-loaded slopes near and above treeline, and give cornices a wide berth as you travel. Continue to keep your eyes peeled for signs of instability like shooting cracks or recent avalanches. 

Avalanche problems

  • Wind Slabs

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

    Fresh wind slabs may form on Tuesday with some more wind and snow still available for transport. Continue to check how the recent couple feet of storm snow is bonding to sun crusts and other interfaces (See discussion below). Shooting cracks or hollow-sounding snow are signs you could trigger an avalanche on similar slopes. Use small test slopes and hand pits to check for instabilities in the upper snowpack. Avoid wind-loaded, leeward slopes and gulies 35 degrees and steeper. Slabs could be deeper and larger as you move up in elevation. Steer around obvious wind features, thickly loaded areas, and unsupported features such as convex rollers. Keep an eye out for overhead hazards such as cornices. If cornices fail, they could create large avalanches or pack a punch on their own.

    Example human triggered wind slab in alpine terrain.

Avalanche Discussion

Winds may pick up a bit at upper elevations on Tuesday. Stay observant, and keep your eyes peeled for signs of wind transported snow and associated instabilities. Southeast to southwest aspects will have a sun crust in the morning that may or may not soften during the daytime.

A large (D2.5), fresh slab avalanche was observed on Saturday on Mount Benzarino. It started at around 6,700ft on a steep southeast aspect and was roughly 200ft wide. We don't know what this avalanche ran on, but in nearby zones we've been finding the sun crust from February 25th to be problematic, and responsible for ski triggered avalanches. On Friday, observers noted a very stormy day, with lots of wind drifting snow. Observers had a close call when a natural avalanche dusted them with a powder cloud from the Cutthroat slide paths on Highway 20. On February 22nd, a strong storm created a widespread, natural avalanche cycle up to size D3 in the area. Most of these were above treeline near the base of cliffs, though some may have been in wind-sheltered terrain. One notable slide was 1-2ft deep and propagated 300ft across. It appears that all avalanches ran within the recent snow or at the interface of new and old snow. 

Persistent slab avalanches are unlikely but could not completely impossible. You are most likely to encounter the structure responsible for persistent slab avalanches in the shallower eastern mountains, and in places that appear heavily wind loaded. Check out Drew's observation from Wolf Creek on Friday. Be sure to check out the forecast for the East Central zone if you are traveling to the southern or eastern edge of this zone for more details on the crust/facet persistent weak layer that is problematic there. 

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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