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 Storm Slabs.
mconlan,
Avalanche Canada
Evaluate terrain carefully and travel conservatively at higher elevations as the latest snow begins to stabilize. Slabs may take longer than typical to bond where they rest on weak or smooth layers.
Summary
Confidence
Moderate
Avalanche Summary
Small to large (size 1 to 2) storm and wind slab avalanches were triggered by riders, explosives, and naturally between Sunday and Wednesday, generally being about 30 cm thick but up to 80 cm thick in wind-loaded areas (as seen here) and primarily at alpine and treeline elevations. Some of the avalanches were triggered by small pieces of cornices failing.
The possibility remains of triggering storm and wind slabs in steep terrain features at treeline and alpine elevations or where this week's storm snow isn't bonding to surface hoar crystals or a smooth crust. Also note that cornices are very large and could fail at anytime.
Snowpack Summary
The region has seen around 50 cm of snow since the weekend, with another 5 to 15 cm expected Thursday night. The wind has been strong to extreme from the southeast to southwest during this time, including for Thursday night. This means that thicker deposits may be found in lee terrain features in wind-exposed terrain.
All this snow may sit on a weak layer of surface hoar crystals on sheltered and shaded treeline and alpine slopes or a hard melt-freeze crust on sun-exposed slopes and on all aspects below 1500 m.
The remainder of the snowpack is well-bonded.
Cornices are large and looming at this time of year.
Weather Summary
Thursday Night
Cloudy with snowfall, accumulation 5 to 15 cm, 50 to 80 km/h southeast wind, treeline temperature -7 °C, freezing level 800 m.
Friday
Cloudy with light snowfall, accumulation 1 to 3 cm, 20 km/h southwest wind, treeline temperature -5 °C, freezing level 1300 m.
SaturdayCloudy with snowfall, accumulation 2 to 5 cm, 20 to 40 km/h south wind, treeline temperature -1 °C, freezing level 1800 m.
SundayCloudy with snowfall, accumulation 5 to 10 cm, 20 to 40 km/h south wind, treeline temperature -3 °C, freezing level 1600 m.
More details can be found in the Mountain Weather Forecast.
Terrain and Travel Advice
- Carefully monitor the bond between the new snow and old surface.
- Be aware of the potential for larger than expected storm slabs due to the presence of buried surface hoar.
- Look for signs of instability: whumphing, hollow sounds, shooting cracks, and recent avalanches.
- Pay attention to cornices and give them a wide berth when traveling on or below ridges.
Problems
Storm Slabs
New snow and strong wind on Thursday night will build on existing storm slabs, which have typically been failing around 30 to 60 cm deep over the past few days. Thicker and touchier slabs may be found in lee terrain features at high elevations. These slabs may take extra time to bond to the snowpack, particularly where they sit on surface hoar crystals or a smooth crust.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Apr 21st, 2023 4:00PM
