Avalanche Forecast

Issued: Nov 20th, 2015 8:00AM

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

danyelle magnan, Parks Canada

Glacier.

It is looking like a beautiful and cold weekend. As the sun lures you out, keep in mind that there are still instabilities in the snowpack. Be careful at ridgecrests where windslabs exist, and avoid thin spots where deep facets may be triggered.

Summary

Weather Forecast

Today should be clear and cold. Temps will be around ~15'C with moderate Northerly winds. Saturday will be slightly warmer, but windier. On Sunday a weather system will bring increasing cloud and flurries by Monday. Freezing levels may rise to 1500m.

Snowpack Summary

Recent observations suggest that the ~1m of storm snow is settling and bonding. Strong S-SW winds at treeline and above continue to load lee features, forming deep loaded pockets. Surface hoar layers down ~1m and 1.5m are still a concern but becoming more stubborn and hard to find. On high elevation N/NE aspects, there is a weak facetted base.

Avalanche Summary

Avalanche activity continued yesterday, but was limited to steep terrain. Several size 2-2.5 slab avalanches were likely triggered by wind-loading. During the major avalanche cycle earlier this week there were avalanches to size 3.5 with some avalanches stepping down to deeper layers, including the Nov 5 surface hoar and the basal facets.

Confidence

Due to the number of field observations

Problems

Wind Slabs

Winds since the storm have been sustained, and there is a lot of new snow for it to transport. Lee features have been loaded, and pockets of windslab exist.

Be careful with wind loaded pockets, especially near ridge crests and roll-overs.

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

2 - 3

Loose Dry

On steep slopes that are sheltered from the wind expect sluffing. Be especially cautious around terrain traps like gullies, or over cliffs.

Be cautious of sluffing in steep terrain.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 2

Deep Persistent Slabs

On northerly alpine slopes, snow from early Sept was preserved and facetted forming a basal weakness. During the storm this week avalanches occurred on this layer. This layer was also responsible for a skier triggered size 3.5 avalanche 10 days ago.

Avoid shallow snowpack areas where triggering is more likely.

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

Elevations: Alpine.

Likelihood

Possible

Expected Size

3 - 4

Valid until: Nov 21st, 2015 8:00AM