Avalanche Forecast
Issued: Apr 20th, 2023 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Persistent Slabs, Loose Wet and Deep Persistent Slabs.
jpercival,
Avalanche Canada
Dangerous avalanche conditions exist in the alpine where new snow continues to incrementally add load to buried weak layers.
Carefully evaluate terrain as you move through the backcountry and when in doubt choose conservative terrain.
Summary
Confidence
Moderate
Avalanche Summary
No new avalanches were reported in the region on Thursday.
Adjacent regions continue to see natural and explosive triggered avalanches, up to size 2, on weak layers.
A fatal avalanche occurred on April 15 in the Thunderwater Lake riding area, just west of this region. The avalanche was triggered near a rocky area and was very large (size 3). Two riders were caught, one was buried approximately 2 meters deep. Despite an immediate extrication rescue response, the rider did not survive. Any additional information we have on this accident can be found in this MIN.
If you are getting out in the backcountry, consider making a post on the MIN (Mountain Information Network).
Snowpack Summary
At treeline and above, 15 - 40 cm of recent snow is being redistributed by variable winds into soft slabs in lees. This overlies a variety of crust, surface hoar and/or facet layers buried in mid March through early April. These interfaces have been the culprit in recent avalanche activity in adjacent regions. Most professional operations in the forecast area are tracking their own local layer of concern to see if they become active with increasing temperatures, or more load from new rain or snow.
Below treeline, expect to find moist or refrozen surfaces, and shrinking snowpack depths.
The mid snowpack is generally settled and strong.
The lower snowpack includes a widespread layer of large, weak facets and/or depth hoar crystals. This weak layer has been responsible for several very large and destructive avalanches throughout the season.
Weather Summary
Thursday Night
Cloudy with isolated flurries, 1-5 cm accumulation. Light southwest ridgetop winds. Freezing levels 500 m. Treeline low around -9 °C.
Friday
Mainly cloudy with isolated flurries, 1-5 cm accumulations. Light to moderate northwest ridgetop wind. Freezing levels 1600 m. Treeline high around -1 °C.
Saturday
Mix of sun and cloud with isolated flurries, trace accumulations. Light to moderate west ridgetop wind. Freezing levels rise from valley bottom to 2000 m by mid-day. Treeline high 0 °C.
Sunday
Mostly cloudy with sunny periods and isolated flurries, 1-5 cm accumulations. Moderate west ridgetop wind. Freezing levels rise from 700 m bottom to 2100 m by mid-day. Treeline high +2 °C.
More details can be found in the Mountain Weather Forecast.
Terrain and Travel Advice
- Brief periods of sun could quickly initiate natural avalanche activity.
- Potential for wide propagation exists, fresh slabs may rest on surface hoar, facets and/or crust.
- Avoid exposure to steep, sun exposed slopes, especially when the solar radiation is strong.
- Avoid thin areas like rock outcroppings where you're most likely to trigger avalanches failing on deep weak layers.
Problems
Persistent Slabs
15-40 cm of dry snow in the alpine overlies a variety of crust complexes that have been reactive in adjacent regions.
A bit of new snow every day is incrementally adding load to these weak layers bringing them closer to threshold. Use extra caution around ridgecrest, small rolls, and on convex slopes. Retreat to mellower terrain if you find signs of instability like shooting cracks, whumpfs, or recent avalanches.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Loose Wet
Be alert to changing conditions when daytime heating and direct sun are impacting slopes. Steep, rocky terrain facing the sun is likely to see thin loose wet avalanches release during the heat of the day.
Aspects: East, South East, South, South West, West.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Deep Persistent Slabs
The base of the snowpack remains very weak. Avoid thin, rocky start zones and shallow areas with variable snowpack depths.
Deep persistent slab avalanches continue to be reported in this forecast area.
This is a low-probability/high-consequence avalanche problem, and managing it is very tricky.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Apr 21st, 2023 4:00PM
