Avalanche Forecast

Issued: Feb 10th, 2017 3:52PM

The alpine rating is considerable, the treeline rating is considerable, and the below treeline rating is moderate. Known problems include Storm Slabs.

Avalanche Canada cgarritty, Avalanche Canada

A combination of sustained snowfall, extreme winds, and rising freezing levels is ramping up avalanche danger in the region this weekend.

Summary

Confidence

Moderate - Forecast snowfall amounts are uncertain on Saturday

Weather Forecast

Friday night: Cloudy with scattered flurries and about 5 cm of new snow. Winds strong to extreme from the southwest.Saturday: Periods of snow delivering 15-25 cm of new snow. Winds extreme from the southwest. Freezing level rising to 700 metres with alpine temperatures around -5.Sunday: Continuing snowfall with 15-25 cm of new snow accumulating. Winds extreme from the southwest. Freezing level to 1100 metres with alpine temperatures around -1Monday: Cloudy with scattered flurries and 5-15 cm of new snow. Winds strong to extreme from the south. Freezing level to 1300 metres with alpine temperatures possibly exceeding 0.

Avalanche Summary

No new avalanches were reported in the past few days. On Saturday, expect a transition from our previous wind slab problem to a more generalized and increasing storm slab problem as new snow accumulates and extreme winds promote rapid slab formation. Keep in mind that a basal weakness continues to drive a low probability/high consequence problem for shallow snowpack areas, especially in the north of the region.

Snowpack Summary

New snow over Friday night will begin to cover the widespread wind affected surfaces that have recently been reported in exposed terrain, including scoured surfaces, sastrugi, and hard wind slabs. In areas sheltered from the wind, the surface snow now being buried was recently reported faceting with surface hoar developing in open areas. Below around 1100 m elevation, a rain crust can be found near the surface of the snowpack. Deeper in the snowpack, the mid-January surface hoar/facet layer is now typically down 70-100 cm. Recent observations suggest the layer has generally stabilized but isolated weaknesses may still exist, especially where buried surface hoar is still intact. Below this layer, the snowpack is generally strong and well settled. The exceptions are areas around Bear Pass and Ningunsaw where basal facets remain an ongoing concern, especially in shallow snowpack areas.

Problems

Storm Slabs

An icon showing Storm Slabs
Fresh storm slabs will begin forming Friday night and over the day on Saturday. Extreme southwest winds will promote rapid slab formation and touchy conditions within the new snow.
Minimize overhead exposure during periods of heavy loading from new snow, wind.Use caution in lee areas in the alpine and treeline. Storm snow is forming touchy slabs.Be cautious as you transition into wind affected terrain.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 2

Valid until: Feb 11th, 2017 2:00PM

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