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Avalanche Forecast

Archived

Dec 12th, 2019–Dec 13th, 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

Northwest Coastal.

Wind slab avalanches are possible in wind loaded areas at upper elevations.

Confidence

Moderate - Forecast snowfall amounts are uncertain.

Weather Forecast

THURSDAY NIGHT: 10-15 cm of new snow, 30 km/h wind from the west, alpine high temperatures drop to -5 C.

FRIDAY: Isolated flurries with up to 5 cm of new snow then clearing in the afternoon, 20 km/h wind from the west, alpine high temperatures around -4 C.

SATURDAY: Mix of sun and cloud, light wind from the west, alpine high temperatures around -6 C.

SUNDAY: Mix of sun and cloud, light wind from the west, alpine high temperatures around -8 C.

Avalanche Summary

A few small wind slab avalanches (size 1) were reported on Thursday morning. Looking ahead, the main concern is new slabs forming above the recently buried surface hoar crystals. Over the next few days the likelihood of triggering storm slab or wind slab avalanches will increase as snow accumulates and settles above this layer.

Snowpack Summary

Stormy weather is burying a concerning layer of surface hoar that formed in areas sheltered from the wind. By Friday afternoon there could 15-30 cm of fresh snow above this layer. As more snow accumulates above this layer expect to it form very reactive slabs. Reports suggest this layer can be found on all aspects up to treeline elevations. In the alpine, the new snow is burying hard wind slabs and sun crusts on south-facing terrain. The lower snowpack is generally considered strong, as there has been very little to report in terms of recent avalanche activity or snowpack test results on deeper layers. Snowpack depths at treeline range from 100-150 cm and taper quickly at lower elevations.

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.