Avalanche Forecast

Issued: Mar 2nd, 2018 4:52PM

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

cgarritty, Avalanche Canada

South Rockies.

A final storm pulse will keep avalanche danger elevated over the weekend. Stick to sheltered, lower angle slopes for the best snow quality and the safest skiing and riding.

Summary

Confidence

Moderate - Forecast snowfall amounts are uncertain

Weather Forecast

Friday night: Continuing flurries bringing up to 10 cm of new snow. Mainly light southwest winds, increasing to strong at ridgetop.Saturday: Continuing flurries bringing about 10 cm of new snow. Mainly light southwest winds, moderate to strong at ridgetop. Alpine high temperatures of -11.Sunday: Mainly cloudy with isolated flurries and a trace of new snow. Light variable winds. Alpine high temperatures of -10.Monday: Mainly cloudy with isolated flurries and a trace of new snow. Light to moderate west winds. Alpine high temperatures around -11.

Avalanche Summary

Over the past week there have been reports of both natural and skier triggered loose dry avalanches in steep terrain, as well as skier and explosive triggered storm slab avalanches up to size 1 that were reported on Monday.Last weekend there were two reports of snowmobilers triggering a size 1.5 and size 2 wind slab releases on northeast to east aspects between 2000-2100 m in the Window mountain area.

Snowpack Summary

About 15-30 cm of new snow now covers previously wind-scoured, westerly slopes and old hard and soft wind slabs on leeward, easterly alpine and treeline slopes. Beneath these old wind slabs lies a well-settled mid-pack. The lower snowpack is weak with two primary concerns that are generally widespread:1) A widespread weak layer from mid-December composed of facets, crusts, and surface hoar that is 100-150 cm deep.2) A rain crust with sugary facets buried in late November near the bottom of the snowpack.

Problems

Storm Slabs

New snow will continue to form storm slabs over Friday night and Saturday. Wind exposed areas will likely see the most rapid slab development and greatest slab reactivity. Loose dry avalanches are a growing concern in steep, sheltered terrain.

If triggered, large wind slabs may step down to deeper layers, resulting in very large avalanchesWatch for signs of instability such as recent avalanches or shooting cracks.Be increasingly cautious as you transition into wind affected terrain.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely - Very Likely

Expected Size

1 - 2.5

Deep Persistent Slabs

Deeply buried weak layers are lingering near the base of the snowpack. These layers are most likely to be triggered from thin or variable snowpack areas or with a large load like a cornice fall.

Pay attention to overhead hazards like cornices which could easily trigger the deep persistent slab.Avoid steep convexities or areas with a thin or variable snowpack.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Unlikely - Possible

Expected Size

2 - 3.5

Valid until: Mar 3rd, 2018 2:00PM