Avalanche forecast

West Slopes North

Northwest Avalanche Center
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Avalanche danger

Sun
Alpine
3 · Considerable
Treeline
2 · Moderate
Below
2 · Moderate
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Highlights

An intense burst of midday snow with wind will elevate avalanche danger, and triggering a large avalanche may be likely. The amount that the danger increases could vary depending on where in the zone you travel, so be prepared to assess new snowfall and how well it bonds to the underlying layer before stepping out on steep slopes. If you notice wind-drifted slabs thicker than 6 inches forming, or notice signs of instability like long shooting cracks or recent avalanches, steer around slopes steeper than 35 degrees during your travels. 

Avalanche problems

  • Wind Slabs

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

    An intense late-morning burst of snowfall accompanied by moderate to strong winds could push the avalanche danger into Considerable in areas of the West North zone. The exact amount of snowfall and wind arriving could turn the table in either that direction, or possibly keep the danger more within the realm of Moderate. If wind-loaded drifts form into large enough pockets, over a foot in depth, then large human-triggered avalanches could occur, and these could be big enough to bury, injure or kill you. If you're looking at shallower drifts, closer to 6 inches in depth, you could still trigger an avalanche, but unless you're near a terrain trap the consequence of being caught in an avalanche will probably be lower. Either way, expect a sharp spike in snow reactivity as the new snow intensifies, and consider reevaluating your travel plans. 

    Pay attention to actively drifting snow, and note where the wind is depositing it. These areas of deposition are locations to avoid if they're on steep slopes. Bullseye clues like long shooting cracks and recent avalanches are in-your-face hints to steer around steep slopes. Expect to find wind slabs in locations beneath ridgelines, around rock outcroppings, in gullies, and on convex rolls. If you're near these features stay on high alert and keep a backup plan in mind as a quick escape from the area. On Friday observers found a potential weak interface, or low-density snow at the surface, which may mean avalanches in the new snow could fail easily on the underlying layer, something to keep in mind while you're out. When in doubt, avoid slopes greater than 35 degrees. 

    (2/17/2021)

    An old photo of a slab avalance in the Bearpaw area, D2 Wind Slab, NE aspect at 5500ft in the West North zone. This is similar to what might occur on Saturday. Photo: Patrick Kennedy

    Photo: Patrick Kennedy

Avalanche Discussion

Friday we saw wet loose avalanche activity (OBSERVATION) and south-facing slopes will be hard and crusty. New snow will probably slide easily on the crust. On other aspects, Saturday's incoming snow will rest over a moderately wind affected 1-2 feet of snow sitting over the MLK crust. The last few days were a rollercoaster, starting with large natural wind slab avalanches propagating widely during the end of the storm which delivered 18"  Tuesday night and Wednesday. A few additional slab avalanches were human-triggered, in addition to elevated concerns, on Thursday (OBSERVATION,  OBSERVATION) before Friday's reports of a snowpack where many of the concerning weaknesses beneath the new snow layer appeared to mainly be healed (wet loose observation). There is still the odd chance that you could trigger an avalanche around two feet deep in a steep, exposed, wind-affected upper elevation area, but that lingering concern is fading. 

 

 

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