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Avalanche Forecast

Archived

Mar 23rd, 2023–Mar 24th, 2023

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

Regions

Northwest Coastal, Kitimat, Nass, Rupert, Seven Sisters, Shames, Stewart, Howson.

Additional snow from the incoming storm is likely to increase reactivity on previously buried surface hoar. Be cognizant of increasing hazard, especially on wind loaded features.

Confidence

Moderate

Avalanche Summary

On Wednesday, avalanche activity had begun to subside as only a few small (size 1) loose wet avalanche were reported that had initiated from very steep south aspect terrain at treeline elevations and below.

On Tuesday, ongoing and continued widespread large (size 2) loose wet avalanches were observed and reported by all operations within the forecast area. These avalanches were at all elevations and confined to mostly south aspect terrain with a few noted cornice collapse occurring.

On Monday, a widespread natural loose wet avalanche cycle was observed, up to 2.5, below treeline. Numerous wet loose avalanches were observed size 1-1.5 on solar aspects at alpine and treeline. Three skier triggered, size 1, windslab avalanches were reported.

On Sunday, two, natural size 3 persistent slab avalanches were observed. Both these avalanches ran to valley bottom and are suspected to have released on a weak layer of surface hoar. Two, size 1.5 persistent slab avalanches were remotely triggered by a helicopter on the same layer.

Snowpack Summary

Upper snowpack continues to settle rapidly as warm temperatures have persisted. Below 1800m moist surface snow exists on all aspects, with a melt freeze crust present on south aspects that extends up to 2000 m.

At elevations treeline and below, a weak layer of surface hoar is found 20-50 cm down in sheltered terrain and continues to be reactive to skier traffic.

A second weak layer of surface hoar and/or faceted grains may be found about 60 cm deep, particularly on shaded aspects near treeline.

The lower snowpack presents as consolidated and strong.

Weather Summary

Thursday Night

Mainly cloudy with snowfall, 1 to 5 cm of accumulation. Light northeast winds at ridgetop. Treeline temperature -3°C. Freezing levels 500 m.

Friday

Cloudy with isolated flurries, trace amounts of accumulation. Light northwest winds at ridgetop. Treeline temperature 0°C. Freezing levels 1000 m.

Saturday

Cloudy with no new precipitation. Light northwest winds at ridgetop. Treeline temperature 0°C. Freezing levels 1000 m.

Sunday

Cloudy with periods of clearing, no new precipitation. Light east winds at ridgetop. Treeline temperature 0°C. Freezing levels 1000 m.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Be carefull around freshly wind loaded features.
  • Carefully assess open slopes and convex rolls where buried surface hoar may be preserved.
  • Potential for wide propagation exists, fresh slabs may rest on surface hoar, facets and/or crust.

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.

Persistent Slabs

Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.