Avalanche Forecast

Issued: Nov 26th, 2015 8:00AM

The alpine rating is moderate, the treeline rating is moderate, and the below treeline rating is low. Known problems include Wind Slabs and Deep Persistent Slabs.

danyelle magnan, Parks Canada

Glacier.

Cold temps have helped to stabilize the snowpack, but sunshine and above freezing temps in the alpine are forecast. Expect the snowpack to be touchier if temps are warming up. The Winter Permit System is now in effect.

Summary

Weather Forecast

A high pressure system will keep the region dry and clear, with light northerly winds through the weekend. Expect cold temps in the valley bottoms, but a temperature inversion is expected to develop with above freezing alpine temps. Valley cloud will likely accompany the inversion.

Snowpack Summary

Strong northerly winds yesterday reverse loaded southerly aspects creating wind slabs. These slabs overlie a variety of surfaces, including suncrust on steep S-SW aspects, with 2-3mm surface hoar on most other aspects. Below this, the snowpack as a whole is strengthening. A weak basal layer exists on alpine N/NE aspects.

Avalanche Summary

Avalanche control yesterday triggered a few slabs to size 2.5. Reverse loading by strong Northerly winds triggered one size 2 slab avalanche as well. A skier-triggered size 2 from a SW aspect, at ~2200m, was reported in the McGill area on Tuesday: 30cm deep, 40m across, running 200m in length.

Confidence

Timing or intensity of solar radiation is uncertain

Problems

Wind Slabs

Expect windslabs to exist where you don't normally find them. Over the past few days, reverse-loading from northerly winds have created slabs on southerly aspects.

Be careful with wind loaded pockets, especially near ridge crests and roll-overs.Be cautious as you transition into wind affected terrain.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

2 - 3

Deep Persistent Slabs

On northerly alpine slopes, snow from early Sept was preserved and facetted forming a basal weakness. This may have been the failure plane on Swiss and Hermit Peak on the weekend.

Avoid shallow snowpack areas where triggering is more likely.

Aspects: North, North East, East, South East.

Elevations: Alpine.

Likelihood

Unlikely - Possible

Expected Size

3 - 4

Valid until: Nov 27th, 2015 8:00AM