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Avalanche Forecast

Archived

Dec 8th, 2020–Dec 9th, 2020

Alpine
Natural and human triggered avalanches likely.
Treeline
Natural and human triggered avalanches likely.
Below Treeline
Natural and human triggered avalanches likely.
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 unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely, human triggered possible.

Regions

Glacier.

The storm came in heavy and warm, and now we are in a natural avalanche cycle.

Avoid any overhead hazard today as we expect avalanches to be running all the way into the valley bottoms.

Weather Forecast

One more storm day, then the weather eases into slightly cooler, sunnier conditions.

Today: Periods of snow, 10-15cm. FZL 1500m, wind SW-25-40km/h

Tonight: Isolated flurries, FZL dropping to 1200m, wind W 10-25km/h

Wed: Mix of sun/cloud, FZL 900m, light W winds

Thurs: mix of sun/cloud, FZL 500m, light W winds

Snowpack Summary

30+cm of warm snow and mod/strong SW winds have created a storm slab. It sits on a significant widespread surface hoar (SH) layer at tree-line and lower elevations. In the alpine, the storm slab rests on a crust on steep solar aspects. Several SH layers exist in the mid-upper pack, while the Nov 5 crust lurks as a deep persistent weakness.

Avalanche Summary

There is an ongoing natural avalanche cycle to sz 3 affecting all elevation bands.

Confidence

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.