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Avalanche Forecast

Archived

Jan 19th, 2022–Jan 20th, 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 unlikely, human triggered possible.
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 potential remains to trigger the deep persistent slab from early December. Stick to conservative terrain while the snowpack adjusts to the new snow load.

Weather Forecast

A frontal system brings snow and warming temperatures Thursday.

Tonight: Scattered flurries (5cm). Alpine low -8*C. Light SW ridgetop winds

Thursday: Snow (15cm). Alpine high -4*C. Freezing level 1400m. Strong gusty SW winds

Friday: Cloudy with isolated flurries. Low -10*C, High -6*C. Light/mod W winds

Saturday: Sunny periods. Low -6*C, High -1*C.

Snowpack Summary

Up to 20cm of new snow and warm temps will build fresh storm slabs over 2-4mm surface hoar.

There are 2 PWLs in the mid-pack: surface hoar is 50-80cm down at and below treeline,a layer of facets from Xmas is down ~100cm.

The Dec 1 crust/facet combo is down ~2-2.5m - this layer came alive last storm, and will be a lingering concern for a long time.

Avalanche Summary

A size 3 deep slab avalanche was triggered by a tree bomb off the shoulder of Abbott on Wednesday.

Neighbors triggered the Dec. 1st crust with heli-bombing on Tuesday.

A large avalanche cycle occurred in the Pass Monday. Size 3-4 avalanches were observed on the W side of the Pass (Fidelity, Camp West, McGill, Smart and Gunners), with crowns over 2m.

Confidence

Freezing levels are 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.

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.

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.