Avalanche Forecast

Issued: Jan 19th, 2020 3:00PM

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 ghelgeson, Avalanche Canada

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In the alpine 10 to 15 cm of snow rests on old wind slabs, sastrugi and wind crust. In sheltered terrain at and below treeline small shallow storm slabs were very sensitive to human triggering over the weekend, a trend that is expected to continue into Monday

Summary

Confidence

Low - Uncertainty is due to the limited number of field observations.

Weather Forecast

While the rest of the province heats up, our region should stay cool through the forecast period. Dribs and drabs of snow are expected to continue through Monday afternoon. Tuesday offers a brief break in the action before another storm system begins to impact the region Wednesday night.

SUNDAY NIGHT: Freezing level around at valley bottom, strong southwest wind, 1 to 5 cm of snow possible.

MONDAY: Overcast at dawn clearing to just a few clouds by sunset, freezing level at valley bottom, moderate southwest wind, 1 to 5 cm of snow possible.

TUESDAY: Scattered cloud cover at dawn building to overcast in the afternoon, freezing level at valley bottom, light to moderate south wind, no significant snowfall expected.

WEDNESDAY: Scattered cloud cover at dawn building to overcast in the afternoon, freezing level at valley bottom, moderate south wind, no significant snowfall expected during the day.

Avalanche Summary

On Saturday thin storm slabs up to 10 cm in depth were sensitive to human triggering at and below treeline where the new snow is resting on facets in wind sheltered terrain.

On Wednesday and Thursday, we received reports of natural and skier triggered wind slab avalanches size 1.5-2.5 around treeline. Crown depths were up to 1 m, and they ran on a surface hoar layer buried by the previous storm on January 10th. 

There have been reports from the Bulkley Valley of natural wind slab and persistent slab avalanches up to size 3. These are thought to have been failing on the crusts/facet/depth hoar interface near the ground. The last reported activity at this interface was Monday January 13th. 

Snowpack Summary

Widespread wind slabs, sastrugi and breakable wind crust can be found above 1400 m. Southerly winds and 10 to 15 cm of recent snow are likely forming fresh wind slabs in places previously scoured by northeasterly arctic outflow winds.

In wind protected features at and below treeline up to 10 cm of recent storm snow lies on top of facets which have recently been sensitive to human triggering. Surface Hoar up to 1 m in depth may also be found at treeline.

Facets, crust and depth hoar can be found near the base of the snowpack. A couple of large avalanches are suspected to have run on this interface in the last few weeks. These larger avalanches have been confined to lee and cross-loaded features in the alpine.

Terrain and Travel

  • Recent wind has varied in direction so watch for wind slabs on all aspects.
  • Watch for areas of hard wind slab on alpine features.
  • Avoid open slopes and convex rolls at and below treeline where weak layers may be preserved.
  • Be aware of the potential for large avalanches due to the presence of a deep persistent slab.

Problems

Wind Slabs

An icon showing Wind Slabs

Widespread wind slabs, sastrugi and breakable wind crust can be found above 1400 m. Southerly winds and 10 to 15 cm of recent snow are likely forming fresh wind slabs in places previously scoured by northeasterly arctic outflows winds.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 2

Deep Persistent Slabs

An icon showing Deep Persistent Slabs

Facets, depth hoar and crust rest near the ground which continue to produce infrequent and yet very large avalanches in alpine features.

Aspects: All aspects.

Elevations: Alpine.

Likelihood

Unlikely - Possible

Expected Size

2 - 3

Valid until: Jan 20th, 2020 5:00PM