Avalanche Forecast

Archived

Mar 12th, 2017–Mar 13th, 2017

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Regions

Kananaskis.

Another large sz 3 in commonly skied terrain was observed on Sunday. See photo. Be aware of large events in the Alpine running full path to the end of their historical runout.

Confidence

High -

Weather Forecast

Over the next few days we can expect a mix of sun and cloud, some light convective flurries and moderate winds out of the SW. When the sun does come out these days it has lots of "punch" and crusts are now being observed on solar aspects.

Avalanche Summary

A sz 3 avalanche was observed on Tent bowl here on Sunday. The avalanche was 240m wide with an average depth of 1m and up to 2m in places failing on the ground. It ran down into mature timber and logged a large amount of new trees. This took out a commonly skied area. There were also 3 Cornice collapses observed on Mt Rundle all resulting in sz 2-2.5 Avalanches that were running to mid path.

Snowpack Summary

Windslabs are being encountered in Alpine areas and in isolated areas such as steep crossloaded gullies at treeline. The biggest concern is the weak basal layers that exist throuhgout the region. These layers just simply cannot be trusted and all larger features should just be avoided until we go through a few solid melt freeze cycles. Thin melt freeze crusts are being found on Solar aspects up to 2400m.

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.

Cornices

Cornice Fall is the release of an overhanging mass of snow that forms as the wind moves snow over a sharp terrain feature, such as a ridge, and deposits snow on the downwind (leeward) side. Cornices range in size from small wind drifts of soft snow to large overhangs of hard snow that are 30 feet (10 meters) or taller. They can break off the terrain suddenly and pull back onto the ridge top and catch people by surprise even on the flat ground above the slope. Even small cornices can have enough mass to be destructive and deadly. Cornice Fall can entrain loose surface snow or trigger slab avalanches.