Avalanche Forecast
Issued: Apr 11th, 2023 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Storm Slabs and Persistent Slabs.
jsmith,
Avalanche Canada
Storm slabs will likely be reactive to human triggers, especially in wind-affected terrain and/or where the recently formed slabs are sitting on weak facets.
Choose conservative terrain and watch for signs of instability.
Summary
Confidence
Avalanche Summary
We are still waiting on observations from the weekend's storm. We are expecting a natural storm slab cycle to have run during the peak of the storm and we wouldn't be surprised to see evidence of large, persistent avalanches as the weather clears.
In the White Pass area on Saturday, a rider triggered a cornice fall from a distance, which produced a size 3 persistent slab avalanche on a northeast aspect at 1750 m. The avalanche was 200 cm deep and was suspected of having failed on a layer of facets above a crust buried in January.
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
30-40 cm of new snow has likely seen some redistribution by southerly winds, forming deep deposits in leeward terrain features. The new snow sits over previously wind-affected snow on north and east-facing slopes and a crust on windward south-facing slopes.
A weak layer of surface hoar/crust/facets buried in early January is now buried well over 1 m deep. This layer has produced recent avalanche activity in the White Pass region and remains a concern in terrain where the snowpack is thin. The lower snowpack consists of basal facets, particularly in shallow areas.
Weather Summary
Tuesday night
Partly cloudy / 20 km/h south ridgetop wind / Temperature at treeline around -12 C
Wednesday
Cloudy with isolated flurries; 0-5 cm / 20 km/h south ridgetop wind / Temperature at treeline around -9 C
Thursday
Mix of sun and cloud / 20 km/h southwest ridgetop wind / Temperature at treeline around -8 C
Friday
Mix of sun and cloud / 20 km/h east ridgetop wind / Temperature at treeline around -8 C
More details can be found in the Mountain Weather Forecast.
Terrain and Travel Advice
- Continue to make conservative terrain choices while the storm snow settles and stabilizes.
- Avoid steep, rocky, and wind effected areas where triggering slabs is more likely.
- Use caution on large alpine slopes, especially around thin areas that may propagate to deeper instabilities.
- Pay attention to cornices and give them a wide berth when traveling on or below ridges.
Problems
Storm Slabs
Storm slabs will likely be reactive to human triggers; especially in wind-affected terrain.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Persistent Slabs
A layer of facets sitting on a crust buried in January has recently been reactive in the White Pass area. Triggering is most likely in areas where the snowpack is thin and weak, or with a heavy load like a cornice fall or the weight of a smaller avalanche in motion triggering this deeper layer.
Aspects: All aspects.
Elevations: Alpine.
Likelihood
Expected Size
Valid until: Apr 12th, 2023 4:00PM
