Avalanche Forecast

Issued: Jan 22nd, 2020 4:00PM

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.

Avalanche Canada kdevine, Avalanche Canada

Email

Recent fresh snow has been redistributed into pockets of wind slab at tree line and in the alpine. Use caution in wind exposed terrain.

Summary

Confidence

Moderate - Uncertainty is due to the fact that deep persistent slabs are particularly difficult to forecast.

Weather Forecast

WEDNESDAY NIGHT - Mainly cloudy with isolated flurries / southwest wind, 20-30 km/h / alpine low temperature near -8

THURSDAY - Cloudy with scattered flurries, up to 5 cm / southwest wind, 30-50 km/h / alpine high temperature near -3 / freezing level 1300 m

FRIDAY - Cloudy with scattered flurries, up to 5 cm / southwest wind, 20-30 km/h / alpine high temperature near -2 / freezing level 1500 m

SATURDAY - Mainly cloudy with scattered flurries / southwest wind, 20-30 km/h / alpine high temperature near -5 / freezing level 1400 m

Avalanche Summary

With strong winds and some fresh snow in the forecast, there could be new wind slabs forming on Thursday and they may become increasingly reactive throughout the day.

Over the past three days there have been a few reports of natural and explosives triggered avalanches up to size 3. A few of these were deep persistent slab avalanches that failed near the base of the snowpack.

There have been no reports of human triggered avalanches over the last three days.

Snowpack Summary

Around 15-20 cm of recent snow over the past week and strong southwest wind has produced wind slabs in lee terrain features. Strong southwest winds on Thursday may form fresh and potentially reactive wind slabs at upper elevations.

A layer of surface hoar that formed in late December appears to be gaining strength. It can be found 70 cm deep around Golden, 30 cm deep around Invermere, 70 cm deep around Kimberley, and 100 cm deep along Kootenay Lake. 

As usual for the Purcells, the base of the snowpack contains basal facets and it remains possible to trigger these deep weak layers in shallow rocky start zones or from a heavy trigger such as a cornice fall or explosives.

Terrain and Travel

  • Avoid freshly wind loaded features, especially near ridge crests, roll-overs and in steep terrain.
  • Use caution on large alpine slopes, especially around thin areas that may propagate to deeper instabilities.

Problems

Wind Slabs

An icon showing Wind Slabs

Fresh wind slabs may form during the day on Thursday and could become more reactive throughout the day with ongoing strong winds and a bit of fresh snow.

Aspects: North, North East, East, South East, North West.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 2

Deep Persistent Slabs

An icon showing Deep Persistent Slabs

Triggering large, deep persistent slab avalanches is a low likelihood but high consequence problem that is most likely in shallow, rocky start zones.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

2 - 3.5

Valid until: Jan 23rd, 2020 5:00PM