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Avalanche Forecast

Archived

Jan 23rd, 2022–Jan 24th, 2022

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

Regions

Glacier.

Over the last week there have been periodic, very large, avalanche events involving the Dec 1st layer, which is a bit unsettling. This is a low probability / high consequence problem that will be lurking in the snowpack for the rest of the season.

Weather Forecast

The upper ridge of high pressure will break down, collapsing the temperature inversion, bringing freezing levels back down to valley bottom. Monday will see mainly cloudy skies with isolated flurries and sunny periods. Freezing level up to 1400m with an alpine high of -6 and 15-35km/hr North Westerly winds. No 'real' snow amounts in the forecast.

Snowpack Summary

Up to 35cm of recent snow now buries the Jan 20th (2-4mm) surface hoar. The Jan 11 (2-5mm) surface hoar is down ~70-90cm. The Dec 1 crust/facet combo is down ~1.5 - 2.5m. Widespread wind affect at tree line and above with pockets of wind slab.

Avalanche Summary

Avalanche Control on Sunday produced results up to size 3, one of which stepped down to the Dec 1st layer. Skiers were trigger small wind slabs up to size 1.5 on steep rolls.

Avalanche Control on Saturday, just West of the Park produced several size 4 - 4.5 avalanches, extending historical trim lines through mature timber.

Confidence

Problems

Wind Slabs

Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind 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.

Deep Persistent Slabs

Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.