Avalanche Forecast

Archived

Apr 17th, 2014–Apr 18th, 2014

Alpine

Natural avalanches unlikely, human triggered possible.

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.

Alpine

Natural avalanches unlikely, human triggered possible.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely.

Regions

Kootenay Boundary.

This bulletin was created using very limited field data. If you are out in the mountains, please send your observations to [email protected]

Confidence

Poor - Due to the number of field observations

Weather Forecast

Tonight and Friday: Cloudy with flurries 5 cm tonight, 5-10 cm Friday. The freezing level is around 1400-1600 m. Winds are light gusting to moderate from the West. Saturday: Cloudy with sunny breaks and a chance of showers. The freezing level rises to 2500 m and ridge winds are moderate to strong from the south. Sunday: Cloudy with sunny breaks and a chance of showers. The freezing level rises to 2200-2400 m and ridge winds are moderate from the west.

Avalanche Summary

There are no reports or recent avalanche activity. On Sunday there was a report of a size 2.5 natural deep persistent slab in the Rossland Range in response to strong solar radiation and warm temperatures. This avalanche released on a steep southeast aspect at around 2100 m and likely failed on the mid February weak layer. It's a good reminder of the potential for large deep avalanches under certain conditions.

Snowpack Summary

10-15 cm of moist new snow (with more expected) sits on a solid and supportive melt-freeze crust on most aspects above around 1600-1700 m. Below this elevation the snow is probably wet. Moderate westerly winds may form new wind slabs in exposed lee and cross-loaded terrain near ridge crests. The late January/early February persistent weak layer is deeply buried and has not produced avalanches in this region for some time now. Cornices are large in some areas and should be given a wide berth.

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.