Avalanche Canada cgarritty, Avalanche Canada

South Rockies Avalanche Forecast

Jan 11th, 2020 4:00PM

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

Conditions vary over the region, with avalanche danger closely linked to wind effect. Seek out low density snow in sheltered areas for the best, safest skiing and riding and be aware of the possibility of slabs forming in more exposed overhead terrain.

Summary

Confidence

High -

Weather Forecast

Saturday night: Cloudy with scattered flurries bringing 5-10 cm of new snow. Moderate southwest winds, becoming strong at ridgetop.

Sunday: Cloudy with continuing flurries bringing 5-10 cm of new snow, continuing overnight. Light to moderate south winds, increasing to strong at ridgetop. Alpine temperatures cooling to around -19.

Monday: Cloudy with isolated flurries and a trace to 5 cm of new snow, continuing overnight. Light southwest winds, becoming strong at ridgetop. Alpine temperatures around -17.

Tuesday: Cloudy with scattered flurries and up to 5 cm of new snow. Light southwest winds, becoming strong at ridgetop. Alpine temperatures around -17.

Avalanche Summary

A few more large (size 2.5) wind slabs were controlled with explosives in the Castle area on Thursday. Observations on Friday were limited by poor visibility and high winds, however several small natural wind slab releases were observed in the same area.

Another notable report on Thursday came from observers witnessing a skier trigger a small wind slab that managed to step down to the basal snowpack to produce a very large (size 3) deep persistent slab. This occurred in a shallow, rocky gully in the Castle area. Its crown fracture was 30-100 cm deep.

Reports from the Castle area on Tuesday and Wednesday showed explosives control yielding storm slab and wind slab releases to size 2.5. Most crown fracture depths were around 40 cm but some larger results were up to 80 cm deep.

Snowpack Summary

The recent storm brought about 25-40 cm of new snow to the region over the early part of this week. In parts of the region, this snow has been redistributed by moderate to strong south and southwest winds in exposed areas at all elevations. Elsewhere it may remain low density and pose a limited hazard.

The recent snow buried older wind slabs and other wind-affected surfaces. This older, wind-affected snow forms the upper part of an increasingly consolidated mid-snowpack, which overlies a generally weak basal snowpack.

The bottom 10-20 cm of the snowpack consists of facets and deteriorating crusts. This basal layer has gradually been gaining strength, but potential still exists for large triggers in thin, rocky areas to trigger avalanches at this depth.

Terrain and Travel

  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Seek out sheltered terrain where new snow hasn't been wind-affected.
  • Avoid freshly wind loaded terrain features.

Problems

Wind Slabs

An icon showing Wind Slabs

Likelihood

Possible-Likely

Expected Size

1 - 2

Our recent snow may react to triggering in dry loose sluffs in sheltered areas, but locally variable winds have redistributed much of this snow into reactive slabs at all elevations and on a wide range of aspects in exposed areas. Keep avoiding thin or variable snowpack areas where a smaller wind slab could trigger a release on our weak basal snowpack.

Aspects:

North, North East, East, South East, North West.

Elevations:

All elevations.

Valid until: Jan 12th, 2020 5:00PM