Avalanche Forecast
Issued: Apr 19th, 2023 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Wind Slabs and Persistent Slabs.
swerner,
Avalanche Canada
Fresh and reactive wind slabs may exist on leeward slopes in the alpine.
Numerous large persistent slab avalanches were triggered by riders in the alpine during the past week. This problem may continue to linger. Choose well-supported, low-consequence lines.
Summary
Confidence
Low
Avalanche Summary
On Wednesday, a glide slab size 2.5 was reported. Reports indicate it happened Tuesday afternoon. A few natural wet loose avalanches were seen up to size 2 from steep solar aspects.
Two persistent slab avalanches were reported northwest of Terrace last Wednesday (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 last Tuesday (11th). It was a skier-triggered size 3 persistent slab avalanche that occurred on a northeast aspect in the alpine.
Observations are limited at this time of year, please consider sharing any information or photos you have on the Mountain Information Network to help guide our forecasts.
Snowpack Summary
10-20 cm of recent snow and strong southeast wind formed wind slabs that may remain reactive to human triggers in isolated locations in the alpine and possibly at treeline. A crust exists up to ridgetop on south-facing slopes and on all aspects up to 1300 m (ish).
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
Wednesday Night
Trace of new snow. Ridgetop winds 40-50 km/h from the southeast. Temperature at treeline around -5 C and freezing level valley bottom.
Thursday
Mostly cloudy. Ridgetop wind 30-50 km/h from the southeast. Temperature at treeline around -3 C freezing level 1300 m.
Friday
Mix of sun and cloud. Ridgetop wind 15-20 km/h from the southwest. Temperature at treeline around -3C with freezing level 1100 m.
Saturday
Cloudy with 5-15 mm of precipitation. Ridgteop wind 30-50 Km/h from the southwest. Temperature at treeline -3 C with freezing levels near 1100 m.
More details can be found in the Mountain Weather Forecast.
Terrain and Travel Advice
- If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
- Potential for wide propagation exists, fresh slabs may rest on surface hoar, facets and/or crust.
- Watch for signs of instability like whumpfing, hollow sounds, shooting cracks or recent avalanches.
- Use conservative route selection. Choose simple, low-angle, well-supported terrain with no overhead hazard.
Problems
Wind Slabs
Fresh wind slabs may be reactive to human triggers on leeward aspects in the alpine.
Aspects: North, North East, East, West, North West.
Elevations: Alpine.
Likelihood
Expected Size
Persistent Slabs
Numerous large persistent slab avalanches have been triggered by riders in the alpine during the past week.
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, Treeline.
Likelihood
Expected Size
Valid until: Apr 20th, 2023 4:00PM
