Avalanche Forecast

Issued: Dec 20th, 2018 4:00PM

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

conrad janzen, Parks Canada

Banff Yoho Kootenay.

New snow, wind and mild temperatures will keep the avalanche danger high on Friday. Natural avalanche activity should decrease over the weekend, but human triggering will remain likely! Avoid traveling in avalanche terrain until things improve.

Summary

Weather Forecast

Snow amounts between 10-20cm are expected Thursday night and into Friday morning with mild temperatures and moderate SW winds. A clearing and cooling trend starts on Friday with a ridge of high pressure building for Saturday and Sunday.

Snowpack Summary

A 40-100cm slab of storm snow now sits over the Dec 10th surface hoar/facet interface at treeline and above, with the snowpack almost doubling in the last week. In many areas the lower snowpack is weak and faceted with the October 26th depth hoar and crusts near the base. Snow pack depths range from 90-160cm at ~2000m.

Avalanche Summary

Numerous natural avalanches up to size 2.5, as well as several skier remote and skier triggered avalanches up to size 2 have been observed in the last several days. This pattern is likely to continue for the next while.

Confidence

Timing, track, or intensity of incoming weather system is uncertain on Thursday.

Problems

Storm Slabs

The recent storm snow has almost doubled our snowpack and is failing easily on the Dec 10 interface. Natural avalanches may reach treeline areas. Safe terrain can be found in low angled forest with no exposure to avalanches from above.

Avoid exposure to overhead avalanche terrain, large avalanches may reach the end of run out zones.Avoid all avalanche terrain.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Very Likely

Expected Size

1 - 2.5

Deep Persistent Slabs

Recent snow has now overloaded the weak middle and lower portions of the snowpack. Avalanches are frequently stepping down to these deeper layers of facets and depth hoar. Avoid traveling in avalanche terrain.

Avoid exposure to overhead avalanche terrain, large avalanches may reach the end of run out zones.Good day to make conservative terrain choices.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely - Very Likely

Expected Size

1.5 - 3

Valid until: Dec 21st, 2018 4:00PM