Avalanche Forecast
Issued: Jan 5th, 2020 4:30PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Wind Slabs and Persistent Slabs.
astclair,
Avalanche Canada
Recent snow and wind are out-pacing the snowpack's ability to adjust. Stay vigilant with simple terrain choices as this pattern continues.
Summary
Confidence
Weather Forecast
Sunday night: Cloudy, 5-10 cm of snow, strong west winds, alpine temperature -10 C.
Monday: Mostly cloudy with isolated flurries, moderate west winds, alpine high temperature -8 C.
Tuesday: Cloudy, 5-10 cm of snow, moderate south winds, alpine high temperature -8 C.
Wednesday: Cloudy, 10-15 cm overnight and through the morning, moderate west winds, alpine high temperature -9 C.
Avalanche Summary
On Friday and Saturday there were reports of small to large (size 1.5-2.5) avalanches releasing from both natural and human triggers on a variety of aspects and elevations. Check out this MIN report and this MIN report for helpful illustrations of this problem. A few avalanches have also been remote-triggered, like this one observed Wednesday. Avalanche activity is beginning to reflect a distinction between smaller, wind-drifted slabs breaking within the storm snow versus larger slabs releasing on the late December surface hoar layer.
Snowpack Summary
The most recent snow has been redistributed by strong winds in exposed areas, loading lee features with stiffer, more reactive slabs.
Over the past week, a total of 60-90 cm of snow has fallen burying a weak layer of feathery surface hoar and a hard melt-freeze crust on sun-exposed aspects. This layer has demonstrated reactivity past its due date as a storm slab interface, and it continues to produce large avalanches across aspects and elevations. Snowpack tests (check out this MIN report from Saturday) have also confirmed this weak layer's propagation potential.
There are a couple more deeply buried weak layers, including a surface hoar layer from mid-December and a facet/crust layer from late November. Despite the significant load from recent snowfall and wind as well as a widespread, large natural avalanche cycle, avalanches have not been observed stepping down to these layers.
Terrain and Travel
- Avoid freshly wind loaded terrain features.
- Be alert to conditions that change with elevation and wind exposure.
- Be aware of the potential for large avalanches due to the presence of buried weak layers.
- Remote triggering is a concern, watch out for adjacent and overhead slopes.
Problems
Wind Slabs
Moderate to strong winds with ample snow for transport over the past 48 hours have formed touchy wind slabs in exposed areas, particularly near ridge features.
Aspects: North, North East, East, South East, South, North West.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Persistent Slabs
60-90 cm of snow has accumulated in the past week over a layer of surface hoar from late December. This layer has demonstrated reactivity past its due date as a storm slab interface and has produced large avalanches across aspects and elevations with incremental loading from new snow and wind. A few of these avalanches were human-triggered remotely from adjacent slopes.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Jan 6th, 2020 5:00PM
