Avalanche Forecast

Issued: Feb 21st, 2018 4:28PM

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

pgoddard, Avalanche Canada

South Rockies.

Caution if the sun comes out - avoid steep sunny slopes where the snow will lose cohesion.

Summary

Confidence

Low - Due to the number of field observations

Weather Forecast

THURSDAY: Mix of sun and cloud with the chance of a flurry. Freezing level at valley floor. Light winds.FRIDAY: Mix of sun and cloud. Freezing level at valley floor. Light winds.SATURDAY: Mix of sun and cloud. Freezing level at valley floor. Light winds.

Avalanche Summary

It's been fairly quiet the last couple of days, with only reports of explosives triggering one size 2 wind slab. On Monday, large (size 2) wind slab avalanches were triggered by skier and explosive activity, 30 to 50 cm deep. A deep persistent slab was also noted in the region, likely releasing on one of the layers described in the snowpack discussion.It is still possible to trigger a wind slab with the weight of a person. If the sun is shining, avoid exposure to steep solar aspects where loose wet avalanche activity is possible.

Snowpack Summary

You are likely to find variable surfaces in open terrain after recent strong winds took out their fury on the upper snowpack. Fragile cornices and hard and soft wind slabs can be found on many alpine and treeline slopes. Ongoing cold temperatures are helping to break down and soften these.A crust/surface hoar interface is about 40-60 cm down, but little is known about its sensitivity and distribution. The lower snowpack in this region is weak with two primary concerns: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.Although the snowpack structure is variable across the region, these persistent weak layers are generally widespread.

Problems

Wind Slabs

Wind slabs may be found on a variety of slopes at and above treeline.

Be cautious as you transition into wind affected terrain.Avoid steep slopes below cornices.Travel on ridgetops to avoid wind slabs on slopes below.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 2

Deep Persistent Slabs

Deeply buried weak layers are most likely to be triggered from thin or variable snowpack areas; or with a large load, like a cornice fall.

Avoid steep convexities or areas with a thin or variable snowpack.Minimize exposure to steep, sun exposed slopes when the solar radiation is strong.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Unlikely - Possible

Expected Size

2 - 3.5

Valid until: Feb 22nd, 2018 2:00PM