Avalanche Forecast

Issued: Dec 25th, 2016 3:00PM

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

Avalanche Canada shorton, Avalanche Canada

Avoid all avalanche terrain. The incoming storm will produce large avalanches.

Summary

Confidence

High -

Weather Forecast

SUNDAY NIGHT: Stormy with 10-20 cm accumulations and extreme southwest winds reaching 100 km/h at ridgetop.MONDAY: Stormy with accumulations of 20-30 cm, extreme 100 km/h southwest winds, temperatures around -10C.TUESDAY: Stormy with accumulations of 10-15 cm, 50 km/h west winds, temperatures around -10C.WEDNESDAY: Flurries with accumulations up to 10 cm, 50 km/h southwest winds, temperatures around -10C.

Avalanche Summary

No new avalanches were reported in the southern part of the region on Saturday. In the northern part of the region, a size 3 avalanche was triggered with explosives. This avalanche failed on weak facets at the base of the snowpack, the same layer that skiers were remotely triggering avalanches on earlier in the week.On Monday, the new snow will form very touchy storm slabs. Storm slabs will be extra reactive in sheltered areas where they are burying a new surface hoar layer. The additional load of the new snow may also reawaken persistent weak layers buried about 1 metre deep. These layers produced large natural avalanches during last week's storm, and now there's some uncertainty as to how reactive they'll be during this storm. If they do release, the resulting avalanches will be very large and destructive.

Snowpack Summary

Expect 20-50 cm of fresh storm snow by Monday afternoon, with extreme winds forming extra deep pockets. The storm snow will bury a layer of feathery surface hoar (up to 15 mm in sheltered areas), making wide propagations possible. A weak interface that formed during the early December cold snap can be found buried about 1 metre deep. The layer consists of weak faceted (sugary) snow, and preserved surface hoar in sheltered areas. The lower snowpack is well consolidated in deep snowpack areas. However, in areas with less snow, such as the northern parts of the region, there are also deeper layers of concern. These include a layer of surface hoar that was buried in mid-November and an old rain crust near the bottom of the snowpack that may have developed weak facets.

Problems

Storm Slabs

An icon showing Storm Slabs
Widespread storm slab avalanches are expected on Monday with heavy snowfall and extreme winds.
If triggered the storm slabs may step down to deeper layers resulting in large avalanches.Avoid all avalanche terrain.Be aware of the potential for large avalanches due to the presence of buried surface hoar.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Very Likely - Certain

Expected Size

1 - 3

Persistent Slabs

An icon showing Persistent Slabs
The additional load of storm snow will make it possible to trigger deeper weak layers that formed during the early December cold snap. These weak layer include facets and surface hoar that are buried over 1 metre deep.
Be aware of the potential for full depth avalanches due to deeply buried weak layers.Avoid all avalanche terrain.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

2 - 4

Valid until: Dec 26th, 2016 2:00PM

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