Avalanche Forecast
Sea To Sky
Expect to see a gradual warming and clearing trend through the weekend.
Avalanche Problem 1: Persistent Slabs
What Elevation?
Which Slopes?
Chances of Avalanches?
Expected Size?
Travel and Terrain Advice
- Avoid open slopes and convex rolls at treeline where buried surface hoar may be preserved.
- Use conservative route selection while travelling at treeline elevations.
Avalanche Problem 2: Wind Slabs
What Elevation?
Which Slopes?
Chances of Avalanches?
Expected Size?
Recent snow and southerly winds have created
Travel and Terrain Advice
- If triggered the wind slabs may step down to deeper layers resulting in large avalanches.
- Be cautious as you transition into wind affected terrain.
- Extra caution needed around cornices with current conditions.
Avalanche Summary
There were no notable avalanches to report Thursday. Reports from Tuesday included a small wind slab on a northwest aspect in the McBride Range stepped down and triggered a much larger persistent slab avalanche when it reached 1900 m. The result was a size 3 avalanche (100 cm thick) that propagated across the entire bowl and ran all the way to the bottom of the valley. A few smaller size 1 natural slabs were also observed at and below treeline.
Several persistent slab avalanches were reported last weekend, including a size 3 avalanche that was remotely triggered on a west aspect at 1900 m in the Blackcomb backcountry and presumably failed on a buried surface hoar layer (see photo and details here). At a similar elevation, a size 2 avalanche failed in a north-facing chute and triggered additional smaller avalanches on nearby slopes. Closer to Squamish, a natural size 2 avalanche failed on a south aspect at 1750 m (see photo and details here). These avalanches highlight a persistent slab problem that exists on all aspects around treeline elevations.
Snowpack Summary
New snow accumulating on Thursday into Friday has been redistributed by southerly winds. This new snow sits on a sun crust on steep south-facing slopes, cold dry snow on northerly aspects, and wind affected snow at upper elevations.
Last week's storms buried a weak layer composed of soft facets, surface hoar, and/or crust that is roughly 50-100 cm below the surface. This layer has produced whumpfing, sudden results in snowpack tests, and some remotely triggered avalanches. Lots of the activity has been on buried surface hoar on north aspects at upper treeline elevations. The snowpack is well settled and strong beneath this interface.
Variable winds in the past month have produced cornices on many ridgelines. They will become touchier as they grow in size, as temperatures rise, and when they are subject to the strong late-winter sun on clear days.
Weather Forecast
FRIDAY: Flurries overnight Thursday into Friday, accumulation 5-10cm then a mix of sun and cloud through Friday / Light west wind / Alpine temperature -5 / Freezing level 800m
SATURDAY: Mix of sun and cloud / light south wind / Alpine temperature -1 / Freezing level 1400m
SUNDAY: Mix of sun and cloud / Light to moderate south wind / Alpine temperature 3 / Freezing level 1900m
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A layer of surface hoar, sugary facets, and/or crust is buried 50-100 cm deep and has produced widespread whumpfing, concerning snowpack test results, and a few large remotely triggered avalanches. Upper treeline elevations are the greatest concern.