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Avalanche Forecast

Archived

Dec 29th, 2018–Dec 30th, 2018

Alpine
Natural avalanches possible, human triggered probable.
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

South Coast Inland.

20-25cm of new snow at upper elevations in the southern portion of the region will require a few days to settle and stabilize.

Confidence

Moderate -

Weather Forecast

SATURDAY NIGHT: Cloudy with isolated flurries and clear periodsĀ  / Moderate northwest wind / Alpine temperature -6 CSUNDAY: Mostly cloudy with sunny breaks / Moderate northwest wind / Alpine temperature -5 C MONDAY: Mix of sun and cloud / Light north wind / Alpine temperature -5 CTUESDAY: Mix of sun and cloud / Light west wind / Alpine Temperature -3

Avalanche Summary

Reports are limited, but no avalanches have been reported in past few days.

Snowpack Summary

20-30 cm of recent new snow covering what is reported to be a widespread weak layer of feathery surface hoar. Below this, about 30 cm of recent storm snow sits on a melt-freeze crust below around 1800 m. Reports are limited, but they suggest that the snow is bonding well to the crust. Expect the deepest deposits of storm snow to be in lee and cross-loaded terrain features.In the north portion of the region and possibly the far south, a weak layer of facets and surface hoar lies below all this storm snow, around 100 to 150 cm deep. The weak layer appears most prominent around treeline, up to 2000 m. There has not been reports of avalanche activity on this layer for the past week. Although this layer is likely gaining strength, field observations show that slab avalanches remain possible on this layer where it exists.

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.