Avalanche Forecast

Issued: Feb 14th, 2020 4:00PM

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

Avalanche Canada cgarritty, Avalanche Canada

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Avoid assuming Saturday's problems are limited to Saturday's new snow. Much more than this is available for wind transport and recent accumulations may become involved in new avalanches through step down activity or entrainment. Stepping back is a good way to manage uncertainty.

Summary

Confidence

Moderate - Forecast snowfall amounts are uncertain.

Weather Forecast

Friday night: Cloudy with flurries bringing about 15 cm of new snow. Strong to extreme southwest winds.

Saturday: Mainly cloudy with easing flurries bringing 5 -15 cm of new snow, easing overnight. Strong west or southwest winds, easing overnight. Alpine high temperatures around -8.

Sunday: Mainly cloudy with scattered flurries and up to 5 cm of new snow. Light southwest or west winds. Alpine high temperatures around -8.

Monday: Mainly cloudy, clearing overnight. Light southwest or west winds. Alpine high temperatures around -8.

Avalanche Summary

Reports from Thursday's storm showed an uptick in avalanche activity, with numerous mainly small (size 1) storm slabs releasing naturally as well as with skier traffic and ski cutting on steeper slopes in the south of the region. Reactivity appeared limited to the depth of overnight snowfall and also reduced by the end of the day. Further north in Bear Pass, stronger winds and greater overnight snowfall led to more significant wind slab activity, with natural releases generally larger than in the south (size 2-3).

A quieter couple days of reports on Tuesday and Wednesday included a few observations of small (size 1) new wind slabs reacting to skier traffic as well as failing naturally on steeper north aspects. On Tuesday many loose wet avalanches up to size 2 (large) were observed running naturally on steep, sun-exposed slopes.

Natural cornice failures have featured regularly in reports from the last week, with some cornices failing to produce avalanches when they impact slopes below, and others producing small wind slabs. 

It's also worth noting that glide slabs continue to release sporadically at lower elevations. A new size 2 glide slab was observed on Wednesday and a size 2.5 natural glide slab avalanche was reported near the Basalt Creek Rest Area east of Prince Rupert on February 7th. It's always a good idea to avoid slopes with glide cracks.

Snowpack Summary

20-30 cm of new snow is expected to accumulate in the region by the end of the day on Saturday, bringing snow totals for this week to about 50-80 cm. In exposed areas, the interfaces within and below this storm snow consist mainly of wind-affected surfaces, but also of sun crusts on south-facing slopes that saw sunshine in between storm pulses. 

In more sheltered areas, the pre-storm surface, expected to be about 40-70 cm deep by the end of the day, is a more varied aspect and elevation-dependant mix of melt-freeze crust (lower elevations), sun crust (sun-exposed slopes), faceted snow and/or surface hoar (shaded aspects).

A thin layer of facets that formed during the January cold snap is now about 120-170 cm below the surface while an early season crust lingers at the base of the snowpack. These layers produced a few large natural avalanches in early February but have more recently been nonreactive.

Terrain and Travel

  • Storm slab size and sensitivity to triggering will likely increase through the day.
  • Recent new snow may be hiding windslabs that were easily visible before the snow fell.
  • Make conservative terrain choices and avoid overhead hazard.

Problems

Storm Slabs

An icon showing Storm Slabs

Lots of new snow has accumulated over the week and 20-30 cm more is on the way for Saturday. Reactivity of the new snow is to be expected, but there is concern for mid and pre-storm interfaces reaching a critical load with the new snow as well. Even if new storm slabs aren't stepping down, they may instead gather mass from recent snow while in motion. Exposed areas where all this new snow has been transported into thick slabs are especially concerning.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Very Likely

Expected Size

1 - 2.5

Valid until: Feb 15th, 2020 5:00PM