Avalanche Forecast

Issued: Nov 27th, 2018 4:16PM

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

kdevine, Avalanche Canada

South Columbia.

The storm is easing off, but avalanche hazard will remain heightened for now. Conservative terrain selection is recommended.

Summary

Confidence

Moderate - Due to the number of field observations

Weather Forecast

TUESDAY NIGHT - Cloudy with isolated flurries, up to 5 cm / light to moderate southwest winds / freezing level 1300-1400mWEDNESDAY - Mainly cloudy with isolated flurries, up to 5 cm / light to moderate southwest winds / freezing level 1400mTHURSDAY - Cloudy with scattered flurries, up to 5 cm / light southwest winds / freezing level 1300mFRIDAY - Cloudy with sunny periods and isolated flurries / freezing level 700-1000m

Avalanche Summary

There have been recent reports of size 1 rider triggered storm slab avalanches at treeline. On Saturday, November 24 a human triggered size 3 avalanche was reported in the region. This avalanche likely ran on the October crust, as it was reported as a full depth avalanche. Two reports on this avalanche can be found on the Mountain Information Network.

Snowpack Summary

The storm that arrived Sunday night has continued to deliver snow over the South Columbia region, bringing total accumulations to anywhere from 40-75 cm by Wednesday morning. This snow sits on top of a weak layer of surface hoar (feathery crystals) and sun crust on steep south facing slopes. The surface hoar is widespread at treeline and below, but it may be found in sheltered alpine areas. At the base of the snowpack is a crust that formed near the end of October. This crust has shown limited reactivity in the South Columbia region, but with recent additional snow, high winds and warm temperatures, this layer could come into play. Snowpack depths taper quickly with elevation, many areas have over 200 cm in the alpine, between 100-160 cm at treeline, and 10-100 cm below treeline.

Problems

Storm Slabs

Widespread storm slabs are sitting on a weak layer of surface hoar (feathery crystals) and sun crust on steep south facing slopes. Expect to find deep deposits on this layer in wind loaded areas.

Be careful with wind loaded pockets, especially near ridge crests and roll-overs.Watch for signs of instability such as whumpfing, cracking, or recent avalanches.If triggered the storm slabs may step down to deeper layers resulting in large avalanches.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

1 - 2

Persistent Slabs

A crust at the base of the snowpack will result in large avalanches if triggered. Storm slab avalanches may have the potential to step down to this layer.

Pay attention to overhead hazards like cornices which could trigger the deep persistent slab.

Aspects: All aspects.

Elevations: Alpine.

Likelihood

Unlikely - Possible

Expected Size

2 - 3

Valid until: Nov 28th, 2018 2:00PM