Avalanche Forecast
Issued: Jan 5th, 2020 3:30PM
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
Continuing snowfall 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, 10-20 cm of snow, moderate west wind with strong gusts, alpine temperature -11 C, freezing level dropping from 1000 m to valley bottom.
Monday: Mostly cloudy, isolated flurries with trace accumulations, light to moderate southwest wind, alpine high temperature -6 C.
Tuesday: Cloudy, 15-25 cm of snow overnight and throughout the day, moderate south wind, alpine high temperature -6 C.
Wednesday: Cloudy, 20-30 cm of snow overnight throughout the day, moderate west wind, alpine high temperature -6 C.
Avalanche Summary
Several human-triggered wind slabs were reported at treeline and alpine elevations on leeward features on Saturday. These avalanches broke 10-40 cm deep and were small in size (size 1-1.5). Additional snowfall and wind transport overnight may increase the size of these slabs on Monday.
Observers also reported large (size 2-3) avalanches breaking on a layer of surface hoar from late December on a variety of aspects and elevations from natural, human, and explosive triggers on Saturday and into Sunday. A few of these avalanches were triggered remotely (i.e. from a distance).
Snowpack Summary
The most recent snow has been redistributed by strong southwest winds in exposed areas, loading lee features with stiffer, more reactive slabs.
Over the past week, a total of 60-100 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.
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
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
50-90 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
