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Avalanche Forecast

Archived

Jan 24th, 2020–Jan 25th, 2020

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

Regions

South Coast Inland.

Triggering avalanches remains likely where new snow and wind has formed storm slabs, especially at higher elevations.

Confidence

Low - Recent weather patterns have resulted in a high degree of snowpack variability within the region.

Weather Forecast

FRIDAY NIGHT: Isolated flurries. Alpine low temperature -6 C. South wind, 15-40 km/hr. Freezing level 1000 m.

SATURDAY: Scattered wet flurries, 5 cm. Alpine high temperature -4 C. South wind 20 km/hr. Freezing level 1500 m.

SUNDAY: Snow, 15-30 cm. Alpine high temperature -3 C. South wind 20-55 km/hr. Freezing level 1400 m.

MONDAY: Scattered flurries, 5-10 cm. Alpine high temperature -4 C. Southwest wind 20 gusting to 50 km/hr. Freezing level 1200 m.

Avalanche Summary

On Friday, small loose wet avalanches failed on south aspects at lower treeline and below treeline elevations.

A large (size 2) deep persistent avalanche failed naturally sometime between Thursday and Friday on north-northwest aspect at 2150 m in the Duffey Lake area. Weak faceted grains and crusts near the base of the snowpack have periodically produced avalanches and continue to be a concern with additional loading from new snow and wind.

On Thursday, small (size 1) storm slab avalanches failed naturally on northerly aspects. Additionally, a machine triggered a size 2 avalanche on a steep slope below a road at 1800 m. Small (size 1-1.5) wet loose avalanche activity was reported below treeline.

Snowpack Summary

New snow, wind and warm temperatures have contributed to storm slab development at treeline and above. As winds impact new, dry snow expect to see scouring and wind loading at upper elevations. Below 1600 m, rising freezing levels and rain produced moist surface snow and rapid snowpack settlement.

There are currently no concerns about deep weak layers in the south of the region (e.g. Coquihalla). There have been two layers of concern in the northern half of the region (e.g. Duffey, Hurley). One is a weak layer of surface hoar buried about 100 cm deep that professionals are tracking at treeline in sheltered areas. The other is weak faceted grains and crusts near the bottom of the snowpack, that is most likely to be triggered in shallow rocky start zones.

Terrain and Travel

  • Storm snow and wind is forming touchy slabs. Use caution in lee areas in the alpine and treeline.
  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Be alert to conditions that change with elevation.
  • Avoid terrain traps such as gullies and cliffs where the consequence of any avalanche could be serious.

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.

Deep Persistent Slabs

Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.