Avalanche Forecast
Issued: Apr 22nd, 2023 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Persistent Slabs and Wind Slabs.
jsmith,
Avalanche Canada
Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
Concern for triggering large persistent slab avalanches remains. Avoid steep, rocky, and wind affected areas where triggering slabs is more likely.
Summary
Confidence
Avalanche Summary
A cornice-triggered size 2 wind slab was reported on a northwest aspect in the alpine on Friday.
Two persistent slab avalanches were reported northwest of Terrace on April 12th. A skier triggered size 2 on a north aspect in the alpine and a size 2.5 on an east aspect in the alpine that was triggered by solar radiation. Both failed on a layer of weak facets and/or surface hoar down 40-50 cm.
A fatal avalanche occurred north of Stewart on April 11th. It was a skier-triggered size 3 persistent slab avalanche that occurred on a northeast aspect in the alpine.
Most professional operations are now closed which means we have very little snowpack or avalanche observation data. Please consider sharing any information or photos you have on the Mountain Information Network to help guide our forecasts.
Snowpack Summary
Strong southerly wind may have formed wind slabs on lee aspects at treeline and above. A crust exists up to ridgetop on south-facing slopes and on all aspects up to approximately 1300 m.
The primary concern is two buried weak layers down 40-140 cm deep in most areas. They include facets and surface hoar in shaded areas and a melt-freeze crust elsewhere. Numerous human-triggered persistent slab avalanches have occurred on these layers during the past week.
The mid and lower snowpack is considered generally strong and well-bonded. In the far northern reaches of the region, basal facets may exist which are currently considered inactive. This layer may become active with abrupt changes to the snowpack, such as rapid loading (heavy snowfall or rain) or prolonged warming.
Weather Summary
Saturday Night
Cloudy with flurries; 3-15 cm (rain below 1000 m) / 30 km/h south ridgetop wind / Temperature at treeline around -1 C / Freezing level 1100 m
Sunday
Mostly cloudy with isolated flurries; 0-5 cm (rain below 1100 m) / 30 km/h south ridgetop wind / Temperature at treeline around 0 C / Freezing level 1300 m
Monday
Cloudy with isolated flurries; 3-5 cm / 40 km/h southwest ridgetop wind / Temperature at treeline around -1 C / Freezing level 1200 m
Tuesday
Mix of sun and cloud with isolated flurries; 0-3 cm / 35 km/h southwest ridgetop wind / Temperature at treeline around -2 C / Freezing level 1100 m
More details can be found in the Mountain Weather Forecast.
Terrain and Travel Advice
- Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
- If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
- Avoid steep, rocky, and wind effected areas where triggering slabs is more likely.
- Watch for signs of instability like whumpfing, hollow sounds, shooting cracks or recent avalanches.
Problems
Persistent Slabs
Numerous large persistent slab avalanches were triggered by riders in the alpine between April 10-12th. Most professional operations are now closed which means we have very little snowpack or avalanche observation data.
The primary concern is a layer of facets and surface hoar buried anywhere from 40-140 cm on shaded slopes. On other slopes, this layer is a crust with facets above. Avoid steep open slopes capable of producing large avalanches.
Aspects: All aspects.
Elevations: Alpine.
Likelihood
Expected Size
Wind Slabs
Strong southerly wind may have formed wind slabs on lee aspects at treeline and above.
Aspects: North, North East, East, West, North West.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Apr 23rd, 2023 4:00PM
