Avalanche Forecast

Issued: Feb 9th, 2020 5:00PM

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

Avalanche Canada MBender, Avalanche Canada

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Broken skies with little precipitation along with winds switching direction will keep wind slabs at upper elevations the main concern.

Summary

Confidence

High - Confidence is due to a stable weather pattern with little change expected.

Weather Forecast

Sunday Night: Cloudy with clear periods. Light to moderate northwest wind. Alpine high temperatures around -10.

Monday: Cloudy with sunny breaks. Light to moderate northwest and west wind. Alpine high temperatures around -7.

Tuesday: Scattered flurries. Light to moderate west wind. Alpine high temperatures around -6.

Wednesday: Mix of sun and cloud. Light to moderate west wind. Alpine high temperatures around -10.

Avalanche Summary

There was a report of a remotely triggered (from a distance) size 2.5 deep persistent slab avalanche. It was 130 cm deep and triggered in a shallow area at 2300 m on a east aspect.

Reports of new avalanche activity Wednesday through Friday were limited to small (size 1-1.5) skier or rider triggered wind slabs along steep ridgetop features.

Reports from Wednesday included three very large (size 3) persistent slab avalanches in the southeastern part of the region, not far from Allan Creek. These avalanches failed naturally on the 150 cm-deep late December surface hoar described in our snowpack summary. They occurred on north and east aspects at around 2300 metres.

Snowpack Summary

20-60 cm of snow from the last week overlies previously wind-affected snow at higher elevations, with diminished depths of about 20-30 cm above a widespread melt-freeze or rain crust up to about 1700 metres. 

The mid and lower snowpack are generally well settled, however an aging weak layer of surface hoar from late December, currently buried 70 to 150 cm deep, has shown surprisingly long-lived instability on slopes between 1700-2400 m (above the crust elevation and below the most wind-affected elevations), warranting increased caution around steeper slopes in this elevation band, particularly in the southern half of the region.

Terrain and Travel

  • Avoid freshly wind loaded features, especially near ridge crests, roll-overs and in steep terrain.
  • Use extra caution around cornices: they are large, fragile, and can trigger slabs on slopes below.
  • Be alert to conditions that change with elevation and sun exposure.
  • Avoid shallow, rocky areas where the snowpack transitions from thick to thin.

Problems

Wind Slabs

An icon showing Wind Slabs

Recent snowfall combined with shifting winds have built wind slabs. Be mindful of areas where wind slab and cornice distribution overlap.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 2

Persistent Slabs

An icon showing Persistent Slabs

A weak layer of buried surface hoar may persist deeper in the snowpack in the south of the region. Easier-to-trigger wind slab avalanches or cornice falls could potentially step down to this persistent slab problem resulting in a very large and destructive avalanches. 

Aspects: All aspects.

Elevations: Treeline, Below Treeline.

Likelihood

Unlikely - Possible

Expected Size

2.5 - 4

Valid until: Feb 10th, 2020 5:00PM

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