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Avalanche Forecast

Archived

Nov 20th, 2020–Nov 21st, 2020

Alpine
Natural avalanches possible, human triggered probable.
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

Little Yoho.

With a slab developing over the Nov 5 crust/facet layer and the continued formation of wind slabs, the snowpack is becoming more complex. Dial back your terrain choices, watch out for rocks, and enjoy the great ski conditions in sheltered areas!

Weather Forecast

Another 5-10 cm is expected on Friday evening before a slight clearing trend on Saturday. Upper winds remain in the moderate to strong range switching from W to NW. Treeline temperatures will be between -10 and -5 C, with temperatures between -12 to -15 C in the alpine.

Snowpack Summary

20-40 cm new snow over the last few days with Mod-Strong SW winds creating wind slabs at treeline and above. The Nov. 5 facet/crust combo near the base of the snowpack is now down 40-80 cm and producing variable test results. The crust extends up to 2500 m on shady aspects and higher on solar aspects. Total snow depths at treeline are 50-110 cm.

Avalanche Summary

Local ski areas were able to trigger multiple new wind slabs in the alpine up to size 1.5 with ski cutting and explosives. On Thursday a skier remote was reported sz 1.5 on facets to ground (40cm deep x 80 m wide) at 2000m near Watermelon peak. One new cornice triggered size 1.5-2 avalanche was observed at ridge top on Mt Rundle

Confidence

Due to the number of field observations

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.

Loose Dry

Loose Dry avalanches are the release of dry unconsolidated snow and typically occur within layers of soft snow near the surface of the snowpack. These avalanches start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-dry avalanches include point-release avalanches or sluffs.