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Avalanche Forecast

Archived

Mar 1st, 2017–Mar 2nd, 2017

Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
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

Cariboos.

Wind slabs will continue to grow at the surface while our deep persistent slab lingers, waiting for the right trigger. Conservative terrain selection is key to managing our complex and increasing hazard.

Confidence

Moderate -

Weather Forecast

Thursday: Cloudy with flurries bringing 5-10 cm of new snow. Winds strong to extreme from the south. Freezing level to 1300 metres with alpine temperatures of -7. Friday: Flurries bringing another 5-10 cm of new snow. Winds moderate to strong from the southwest. Freezing level to 1000 metres with alpine temperatures of -8. Saturday: A mix of sun and cloud with isolated flurries and a trace of new snow. Winds light from the south. Freezing level back to valley bottom with alpine temperatures of -10.

Avalanche Summary

No new avalanches were reported on Tuesday.Many parts of the region have a similar snowpack structure to Clemina Creek, where two size 2 snowmobile triggered persistent slab avalanches were reported on Saturday (see MIN report here). On Monday, another size 2 persistent slab avalanche was accidentally triggered by a skier northwest of Valemount. Nobody was injured in the avalanche which was 50cm deep at the crown and about 120m long. Triggering a large deep persistent slab avalanche is a low probability - high consequence scenario that warrants an extra cautious approach to terrain. See here for a list of recent near misses in the Cariboos and North Rockies.Looking forward, ongoing snowfall and increasing winds on Thursday are expected to promote new wind slab activity at treeline and in the alpine.

Snowpack Summary

About 10-15cm of new snow fell over the region Tuesday night, accompanied (and affected) by strong overnight winds. The new snow has buried faceted surface snow, as well as surface hoar recently reported in sheltered areas in some parts of the region. A thin sun crust may also exist below the new snow on steep solar aspects. About 40cm below the surface you'll likely find the mid-February interface, which is composed of a thick rain crust up to about 1700 m, sun crusts on steep solar aspects, and spotty surface hoar on shaded aspects. The reactivity of this layer is unknown, but it's worth keeping an eye on as it gets loaded by more snow. Some lingering surface hoar layers from January are down about a metre and the weak mid-December facets are down about 1.5 metres. These deep persistent weaknesses still have the potential to react to human triggers.

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.