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Avalanche Forecast

Archived

Jan 25th, 2020–Jan 26th, 2020

Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.

Regions

Northwest Coastal.

Triggering avalanches remains likely where strong winds have drifted the recent snow into slabs at higher elevations. Stay alert and monitor for these conditions if travelling in these areas.

Confidence

Moderate - Uncertainty is due to rapidly fluctuating freezing levels.

Weather Forecast

Saturday night: Cloudy, scattered flurries with 2-5 cm of snow possible, strong south winds, alpine temperature -2 C, freezing level around 1000 m.

Sunday: Cloudy, 2-5 cm new snow, 10-15 cm near Kitimat, strong south winds, alpine high temperature -2 C, freezing level around 800 m.

Monday: Mostly cloudy, 10-15 cm near Terrace, 20-30 cm near Kitimat, moderate southwest winds, alpine high temperature -3 C, freezing level around 500 m.

Tuesday: Mix of sun and cloud, light south wind, alpine high temperature -5 C, freezing level around 200 m.

Avalanche Summary

Over the past 48 hours, numerous natural loose wet avalanches in steep terrain up to size 2 were observed up to 1000 m. Small pockets of human-triggered wind slab were reported at treeline elevations closer to Terrace, while larger (size 2-3.5) wind slabs were reported further north in the Bear Pass area releasing naturally from alpine start zones.

Reports of deep persistent slab avalanches have been trickling in throughout the month, with the last reported event occurring on Jan 17th. They are associated with a November crust layer near the base of the snowpack which has produced very large avalanches (size 3+) with crown depths of around 2 m. These have typically run in alpine terrain, on lee or cross-loaded slopes. Recent loading has been a good test for this layer and it seems to be trending less reactive.

Snowpack Summary

Around 1 m of recent storm snow is settling rapidly. A rapid warm-up moistened snow surfaces up to 1400 m, which was described as "a thigh-burning, elephant snot mix of coastal pow-tatoes" in this MIN report

In exposed areas above 1400 m, strong southerly winds are building wind slabs on north facing slopes. The new snow rests on extensively wind affected surfaces at upper elevations and a thick layer of weak facets in sheltered areas near treeline and below.

A crust from mid November lurks at the base of the snowpack. The last reported avalanche on this layer was Jan 17th, and it will most likely require a large trigger such as explosives or cornice fall to initiate this deep persistent slab problem.

Terrain and Travel

  • Be careful with wind slabs, especially in steep, unsupported and/or convex terrain features.
  • Expect slab conditions to change drastically as you move into wind exposed terrain.
  • Stay off recently wind loaded slopes until they have had a chance to stabilize.

Problems

Wind Slabs

Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.