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Avalanche Forecast

Archived

Jan 16th, 2014–Jan 17th, 2014

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 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, human triggered possible.

Regions

Kootenay Boundary.

Forecast very warm temperatures are an added concern to a complex snowpack.

Confidence

Fair - Timing or intensity of solar radiation is uncertain

Weather Forecast

Overnight and Friday: A warm and dry airmass I expected to move into the Interior mountains overnight. Expect very warm alpine temperatures with above freezing up to about 3000 metres by the afternoon. Winds should diminish to light Westerly during the day. Clear skies should add strong solar radiation to the already warm air.Saturday: Continued very warm alpine temperatures with light winds and mostly clear skies. Becoming cloudy in the evening and cooling to near freezing.Sunday: Mix of sun and clouds with moderate to strong Westerly winds and freezing levels near 2000 metres.

Avalanche Summary

One natural avalanche size 3.0 was reported from the North of the region that released close to the ground, suspect basal facets. Some natural cornice falls to size 2.0 and explosive control up to size 3.0 near Nelson. The size 3.0 avalanche released down to the weak layer of facets near the ground (Basal facets), and was up to 3 metres deep. Some loose wet avalanches were reported from steep solar aspects to size 1.0 in the highway corridor.

Snowpack Summary

The North of the region received more storm snow over the past week than the rest of the region. The storm slab in the North is close to a metre thick and appears to be more touchy than in most of the rest of the region. The Rossland range has a shallower snowpack and weak basal facets continue to be a concern where wind slabs and storm slabs have added load above the weak layers. The forecast very warm alpine temperatures may result in a period of fairly rapid warming of wind and storm slabs above loose weak layers. Periods of strong solar radiation may cause moist or wet loose snow avalanches and/or cornice falls which may result in large additional loads above deeply buried weak layers.

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.

Persistent Slabs

Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.

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.