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Avalanche Forecast

Archived

Jan 18th, 2022–Jan 19th, 2022

Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches possible, human triggered probable.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches possible, human triggered probable.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches possible, human triggered probable.

Regions

Glacier.

The weak layers deep in the snowpack awoke Monday night, resulting in very large avalanches in very skiable terrain.

Minimize your overhead exposure, especially during periods of direct sunshine on steep slopes above.

Weather Forecast

Some strong sun, some snow, then an alpine temp inversion for the weekend.

Tonight: Mainly clear, Alp low -10*C, light winds

Wed: Sun and cloud, Alp high -9*C, light SW winds

Thurs: Snow, 15cm, Alp high -6*C, strong gusty SW winds

Fri: Cloudy with isolated flurries, Alp high -7*C, light/mod W winds

Snowpack Summary

40-50cm of new snow, warm temps, and strong S'ly winds built a widespread surface storm slab. This sits upon a surface hoar layer at and below treeline, ~50-80cm down, with sugary facets from Xmas below this. Under all this, the Dec 1 crust/facet combo lurks ~2-2.5m below the surface and was woken up by this last storm load.

Avalanche Summary

A large avalanche cycle occurred in the Pass Monday. Numerous sz 4 avalanches, clearing mature timber, were observed on the W side of the Pass. Deep crown lines were observed Tues am, suggesting the deep persistent weak layer from Dec 1 finally couldn't hold the snowload. Fidelity, Camp West, McGill, Smart, Gunners all had big avalanches to sz 3-4.

Confidence

Timing or intensity of solar radiation is uncertain

Problems

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.

Persistent Slabs

Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.