Avalanche Forecast

Issued: Dec 20th, 2019 5:00PM

The alpine rating is high, the treeline rating is high, and the below treeline rating is high. Known problems include Storm Slabs, Loose Wet and Persistent Slabs.

Avalanche Canada MBender, Avalanche Canada

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Continued loading from snow and wind Friday night through Saturday will keep the avalanche danger at HIGH.

Summary

Confidence

Moderate - Forecast snowfall amounts are uncertain.

Weather Forecast

Friday Night: Snow, accumulation 15-25 cm. Alpine temperature -3 C. Moderate to strong southwest wind. Freezing level 1600 m.

Saturday: Snow, accumulation 15-30 cm. Alpine temperature -2 C. moderate to strong southwest wind. Freezing level 1700 m.

Sunday: Flurries, 5-10 cm. Alpine temperature -3 C. Moderate southwest wind. Freezing level 1000 m.

Monday: Mix of sun and cloud. Alpine temperature -4 C. light southwest wind. Freezing level 1000 m.

Avalanche Summary

Expect a natural avalanche cycle to be ongoing through Saturday as slabs build due to heavy loading from snowfall, wind and warm temperatures. On Friday there were reports of widespread avalanche activity in the recent storm snow.

On Wednesday, two large natural avalanches in the Morrissey area were reported to have failed on a crust from mid-November. A cornice failure triggered a size 2.5 avalanche, and one size 2 slab avalanche failed naturally, both avalanches had crown depths 70-100 cm, were on east-northeast aspects, and suspected to have been triggered by strong winds.

Snowpack Summary

Snowfall at upper elevations has covered a previously variable and wind-affected surface and is expected to build and develop reactive storm slabs. Expect the surface snow at lower elevations to be moist due to rain.

Crust layers from November and October can be found 40-100 cm below the surface. These layers produced large avalanches with explosive triggers around Dec 13-14, but since then have appeared to gain strength, but may become overloaded with incoming snow.

Snowpack depths range between 60-130 cm at higher elevations and taper rapidly below treeline.

Terrain and Travel

  • Avoid all avalanche terrain during periods of heavy loading from new snow and wind.
  • Avoid exposure to overhead avalanche terrain, avalanches may run surprisingly far.
  • Storm slabs in motion may step down to deeper layers resulting in large avalanches.

Problems

Storm Slabs

An icon showing Storm Slabs

Touchy storm slabs will build through Friday night and Saturday due to heavy loading from snowfall, wind and warm tempertures.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Very Likely - Almost Certain

Expected Size

1.5 - 2.5

Loose Wet

An icon showing Loose Wet

 Expect to see loose wet avalanches in steep terrain at lower elevations due to rain. 

Aspects: All aspects.

Elevations: Treeline, Below Treeline.

Likelihood

Likely - Very Likely

Expected Size

1 - 2

Persistent Slabs

An icon showing Persistent Slabs

A weak layer that formed as a crust in mid-November persists in the region. This layer may wake as rapid loading from new snow, wind, or smaller storm slab avalanches stresses deeper instabilities, resulting in larger and more destructive avalanches.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

2 - 3

Valid until: Dec 21st, 2019 5:00PM