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 Wind Slabs and Persistent Slabs.
jsmith,
Avalanche Canada
Fresh wind slabs may be reactive to human triggers on lee aspects in the alpine.
Avoid steep, rocky, and wind affected areas where triggering slabs are more likely.
Summary
Confidence
Avalanche Summary
A naturally triggered size 2 wind slab was reported on a northeasterly aspect in the alpine on Thursday. See MIN.
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 on lee aspects at treeline and above. A crust exists up to ridgetop on south-facing slopes and on all aspects up to approximately 1500 m.
A weak layer buried in late March is down 30-50 cm and exists as surface hoar and facets on north-facing slopes and a crust elsewhere. Test results show that this layer may be reactive to human triggers in isolated locations on north-facing slopes where the layer is well-preserved and have a cohesive overlying slab.
The middle of the snowpack is strong and contains numerous hard crusts. Near the ground, weak faceted crystals exist. There hasn't been avalanche activity on this layer recently, but it remains on our radar and may become active when we experience change, such as rapid loading (heavy snowfall or rain) or prolonged warming.
Weather Summary
Thursday Night
Mostly cloudy with isolated flurries; 3-15 cm / 30 km/h east ridgetop wind / Temperature at treeline around -4 C / Freezing level 600 m
Friday
Mix of sun and cloud with isolated flurries; 0-10 cm / 20 km/h southeast ridgetop wind / Temperature at treeline around -2 C / Freezing level 1500 m
Saturday
Cloudy with flurries; 5-10 cm / 30 km/h south ridgetop wind / Temperature at treeline around -3 C / Freezing level 1300 m
Sunday
Cloudy with isolated flurries; 0-10 cm / 20 km/h southeast ridgetop wind / Temperature at treeline around -1 C / Freezing level 1600 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.
- Avoid steep, rocky, and wind effected areas where triggering slabs is more likely.
- If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
- Watch for signs of instability like whumpfing, hollow sounds, shooting cracks or recent avalanches.
Problems
Wind Slabs
Fresh wind slabs may be reactive to human triggers on lee aspects at treeline and above.
Aspects: North, North East, South West, West, North West.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Persistent Slabs
30-50 cm of snow sits above a layer of facets and surface hoar on shaded slopes. On other slopes, this layer is a crust with facets above. Whumfing and settlements in the upper snowpack have been reported on this interface as well as snowpack test results indicating that human-triggering this slab is possible. Avoid steep open slopes capable of producing large avalanches.
Aspects: All aspects.
Elevations: Alpine.
Likelihood
Expected Size
Valid until: Apr 21st, 2023 4:00PM
