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Avalanche Forecast

Archived

Dec 16th, 2019–Dec 17th, 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

Banff Yoho Kootenay.

Increased wind and small amounts of new snow are creating new reactive wind-slabs at ridge top.

Weather Forecast

Seasonal temps (-5 in the valley, -10 at the ridge) for the next few days. Light snow is expected totalling 10cm by Thursday midday. Ridgetop wind is expected to be in the strong to extreme range from the W-SW on Tuesday afternoon. Some more significant snow is expected on the weekend, but the outlook is still uncertain.

Snowpack Summary

Reactive, thin (~10cm) new windslabs are being created by increased west wind. Beneath the recent 40-60 cm of storm snow, the snowpack structure is generally weak, consisting of facets and depth hoar. The Nov crust is present up to 2500m and ~30 cm up from ground. Snowpack depths at treeline range from 80-160 cm.

Avalanche Summary

Small windslabs (size 1) were reported near Mt Ogden today. They likely occurred within the last 24 hours. Additionally, a small wind slab was triggered by 2 ice climbers on the half way ledge on Bourgeau Left today.

Confidence

Wind effect is extremely variable on Tuesday

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.

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.