Avalanche Forecast

Archived

Feb 13th, 2020–Feb 14th, 2020

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches possible, human triggered probable.

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.

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely.

Regions

Kananaskis.

The winds have blown around the recent snow and formed wind slabs almost everywhere. They range in density, but generally they get harder/more reactive near ridges. They will take a day or two to settle out. In the mean time, the skiing is still good in sheltered areas.

Confidence

High -

Weather Forecast

Overnight lows will settle around -12 by early morning. The day time high will hit -9 by mid afternoon. Flurries will bring trace amounts of snow. Treeline winds will be moderate, gusting to strong (44km/hr) from the west.

Avalanche Summary

We did see some wind induced activity today. Little Tent ridge had soft slabs fail on east aspects. They were sz1.5, started in the alpine and ran to mid track.

There was also a sz2.5 on Old Goat Mountain that started with a small cornice failure. The resulting windslab pulled a larger pocket to ground. It was a south aspect, on a high, unsupported alpine slope.

Snowpack Summary

No new snow last night, but we sure got the winds! This morning they were strong and from variable directions at treeline and alpine. By mid afternoon they atleast settled to a SW flow, but still raged. There are new windslabs everywhere, either because of lee loading or crossloading. Steep, unsupported slopes were cracking today, but tough to get going in ski cuts. Other than that the midpack has no change with the bottom 30cm still rotten and weak depth hoar. HS at 2200m 150cm. Cornices have quickly developed and will likely shed as the winds continue.

Terrain and Travel

If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.

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.