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Avalanche Forecast

Archived

Dec 2nd, 2020–Dec 3rd, 2020

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

Regions

Little Yoho.

Lots of good observations today, and overall the sun didn't destabilize the snowpack as much as we thought it might have. Thursday and Friday look cooler, but still a good idea to minimize your exposure to steep solar terrain in the heat of the day.

Weather Forecast

The alpine inversion (warmer temperatures in the alpine than the valley bottom) will continue on Thursday but be less severe. Winds are forecasted to pick up Thursday afternoon, and temperatures will cool further on Friday (although remain warm). No precipitation forecast in the next 3 days. Overall, mild and dry conditions.

Snowpack Summary

Variable surface conditions exist with hard wind slabs in exposed locations, softer snow in more sheltered areas and a surface crust on some solar aspects. The Nov 5 facet/crust combo is down 50-80 cm and producing hard to no results. This crust extends up to 2500 m on N aspects and higher on solar aspects. Snow depths at treeline are 70-140 cm.

Avalanche Summary

Despite warm alpine temperatures and sun, very little activity was noticed on Wednesday. Some small wet loose pinwheeling up to size 1 out of steep solar terrain in the afternoon, but overall fairly minimal activity with lots of good observations in the southern Wapta / Yoho Valley area.

Confidence

Timing or intensity of solar radiation is uncertain

Problems

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.

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.