Avalanche Forecast

Issued: Nov 27th, 2018 4:20PM

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.

kdevine, Avalanche Canada

North Columbia.

The storm may be easing off, but avalanche hazard remains heightened. Conservative terrain selection is advised.

Summary

Confidence

Moderate - Due to the number of field observations

Weather Forecast

TUESDAY NIGHT - flurries, up to 5 cm / moderate southwest winds / freezing level 1300-1500mWEDNESDAY - Cloudy with isolated flurries, up to 10 cm / light to moderate southwest winds / freezing level 1300-1500mTHURSDAY - Cloudy with sunny periods and isolated flurries / light south winds / freezing level 1100mFRIDAY - A mix of sun and cloud / light southwest winds / freezing level 900-1100m

Avalanche Summary

Several size 1 rider triggered storm slab avalanches were reported on Monday afternoon.Of note, a size 3 human triggered avalanche that likely ran on the October crust was reported on Saturday, November 24 in the South Columbia region. The avalanche reportedly occurred on a northwest aspect, on a lee feature in the alpine. The full report can be found on the Mountain Information network. Click here to read the report

Snowpack Summary

Ongoing snowfall since Sunday night brings total recent storm snow amounts to 35-90 cm by Wednesday morning. This new 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 most pronounced at treeline and below, but it may be found in sheltered alpine areas.At the base of the snowpack is a crust that formed in late October. There have been no reports of reactivity on this layer in the North Columbia region, however with recent snow, winds and high freezing levels, this layer could come into play. Total snowpack depths vary greatly with elevation. Recent reports show depths of 120-210cm in the alpine, 80-150 cm at treeline and 10-120 cm below treeline.

Problems

Storm Slabs

Widespread storm slabs sit on a weak layer of surface hoar (feathery crystals), and sun crust on steeper south facing slopes. Expect to find deep deposits of snow over 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, and recent avalanchesIf triggered, the storm slabs may step down to deeper layers resulting in large avalanches.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

1 - 2

Deep 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.Minimize overhead exposure during periods of heavy loading from new snow, wind.

Aspects: All aspects.

Elevations: Alpine.

Likelihood

Unlikely - Possible

Expected Size

2 - 3

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