Avalanche Forecast

Issued: Dec 9th, 2019 4:00PM

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

Avalanche Canada ahanna, Avalanche Canada

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There is uncertainty with the reactivity of several buried weak layers which have produced large avalanches recently. Although avalanche activity related to last week's storm has slowed, use caution when pushing out into more complex terrain.

Summary

Confidence

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

Weather Forecast

Monday Night: Cloudy with clear periods, alpine low -11, moderate northwest wind.

Tuesday: Cloudy with sunny periods, temperature inversion to 2500 m with alpine temperature -6, moderate west wind.

Wednesday: Cloudy with sunny periods and isolated flurries, alpine temperature -6, moderate west wind increasing into the night.

Thursday: Cloudy with sunny breaks and flurries accumulating to 5 cm, alpine temperature -5, moderate southwest wind.

Avalanche Summary

There have only been a handful of field observations in the region to date. Many of the reported avalanches in the previous storm cycle released on the weak layer buried in late November. One such avalanche was a size 2.5 observed on Sunday on a southeast aspect at 2500 m. The natural avalanche cycle that coincided with snowfall late last week has likely slowed down but it is important to keep in mind the potential for large, deep avalanches.

Snowpack Summary

40-80 cm of new snow from late last week has covered a layer of feathery surface hoar that has been found at all elevations. This surface hoar sits on soft snow that fell shortly before its formation (early last week) and was covered shortly after (mid last week). It may soon settle out, but for now we will continue to watch for it. Below, a thick layer of faceted crystals, previously wind-affected surfaces, and/or surface hoar in sheltered areas (around treeline and below) is now 60-90 cm below the surface.

An additional layer of surface hoar may be found in sheltered areas around treeline down 70-120 cm. In some areas this may sitting on a thin crust. A variety of crusts from late October are buried deeper in the snowpack.

Problems

Storm Slabs

An icon showing Storm Slabs

In some areas, the storm slab may harbor a layer of weak, feathery surface hoar crystals formed during the mid-week break in the storm last week.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

1 - 2

Persistent Slabs

An icon showing Persistent Slabs

A surface hoar/crust layer, down 60-90 cm may be found in some parts of the region. This layer is most likely found in sheltered openings.

Aspects: All aspects.

Elevations: Treeline, Below Treeline.

Likelihood

Possible

Expected Size

1 - 2.5

Valid until: Dec 10th, 2019 5:00PM

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