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Avalanche Forecast

Archived

Dec 10th, 2019–Dec 11th, 2019

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

Regions

Glacier.

Wind slabs and persistent slabs have surprised a number of people recently, especially on S'ly aspects where they overlay a crust. Give steep southern slopes respect!

Weather Forecast

A mix of sun and cloud today, alpine high of -4*C with light SW winds and fzl rising to 1200m. Wednesday brings light flurries and light SW winds with an alpine high of -7*C. Thursday a cold front passes through the area, delivering 10cm of snow, moderate SW winds, and an alpine high of -5*C.

Snowpack Summary

Moderate S-SW winds have created wind slabs in lee alpine features. 40cm of storm snow (since Dec. 5th) overlies surface hoar in some locations TL and BTL, and is concealing evidence of the recent cycle of natural avalanches. The November 23rd surface hoar/crust/facet layer is buried 80-100+cm and remains reactive in stability tests.

Avalanche Summary

Natural avalanche activity has tapered off, but observations of several human triggered avalanches to sz 2 were made yesterday. A skier kicked off a sz 2 wind slab from a steep, S-facing alpine start zone on Tupper. Another sz 2-2.5 was reported from SE slopes on Ursus Major at around 2500m elevation. Both slabs likely failed on a crust.

Confidence

Problems

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.

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.