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Avalanche Forecast

Archived

Mar 12th, 2024–Mar 13th, 2024

Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches possible, human triggered probable.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches possible, human triggered probable.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural and human triggered avalanches likely.
Below Treeline
Natural and human triggered avalanches likely.

Regions

Glacier.

Reactive storm slabs are present where wind has stiffened the snow surface at Alpine and Tree-line elevations.

The strong Spring sunshine and warm temps will actively trigger avalanches on sunny slopes in the upcoming days.

Remote triggering of large avalanches is still a concern with a robust crust lurking ~1m below the surface.

Confidence

Moderate

Avalanche Summary

Natural avalanche activity in the hwy corridor has corresponded with wind spikes in the unsettled weather the last few days. Numerous avalanches up to sz 3 were observed Monday both E and W of the Pass. These were believed to be running in the new storm snow or on the reloaded Feb 3 bed surface.

Last Thursday, we observed naturally-triggered size 3 slab avalanches from Catamount Mtn SE face and Mt. Leda NE face. These were both deep, likely failing on the Feb 3rd crust.

Snowpack Summary

A 30-40cm storm slab now rests upon variable old surfaces: a thin suncrust on South & West aspects; previous wind effect from variable winds in open terrain; and settled powder in sheltered areas.

80-140cm of settled snow sits atop a sugary facet layer. These facets are not bonding well to the widespread, very firm crust from Feb 3rd. This crust is a significant persistent weak layer and will be the main layer of concern for the foreseeable future.

Weather Summary

A ridge builds over BC, resulting in clearing skies, slackening winds, and rising freezing levels (FZL).

Tonight: Clear periods, isolated flurries, trace, low -9°C, light W winds, FZL 500m.

Wed: Mix of sun/cloud, Alp high -8°C, light W winds, FZL 1300m.

Thurs: Sun/cloud, Alp high -1°C, light W winds, FZL 1600m

Fri: Sun/cloud, Alp high 4°C,, light NW winds, FZL 2800m

Terrain and Travel Advice

  • Watch for fresh storm slabs building throughout the day.
  • Use conservative route selection. Choose simple, low-angle, well-supported terrain with no overhead hazard.
  • Remote triggering is a concern, avoid terrain where triggering slopes from below is possible

Problems

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.