Avalanche Forecast
Sea To Sky
A buried weak layer is capable of producing large human-triggered avalanches. Be aware of signs of instability such as whumpfing and stick to small supported terrain features.
Avalanche Problem 1: Persistent Slabs
What Elevation?
Which Slopes?
Chances of Avalanches?
Expected Size?
Travel and Terrain Advice
- Use caution on open slopes and convex rolls at treeline where buried surface hoar may be preserved.
- Choose well supported terrain without convexities.
- Minimize exposure to steep, sun exposed slopes when the solar radiation is strong.
Avalanche Problem 2: Cornices
What Elevation?
Which Slopes?
Chances of Avalanches?
Expected Size?
Continued snowfall and strong wind from around the clock has formed large cornices on many ridgelines. Cornices are inherently unstable, unpredictable, and demand respect, especially when the sun is out.
Travel and Terrain Advice
- Firm cornices may pull back into flat terrain at ridgetop if they fail.
- Give cornices a wide berth when traveling on or below ridges.
- Be careful with wind loaded pockets
Avalanche Summary
On Sunday, a MCR report from the Blackcomb backcountry has a picture of a large remotely triggered avalanche (see here). This size 3 avalanche occurred on a west aspect around 1900 m and presumably failed on the buried surface hoar layer. A few similar, but slightly smaller, avalanches were reported in nearby terrain at similar elevations and on a range of aspects. This persistent weak layer will likely remain reactive to human triggers throughout the week.
On Saturday, a few natural size 1-2 slabs were reported on north aspects and numerous wet loose avalanches were reported on steep south-facing terrain. Several small snowmobile triggered avalanches (size 1) were reported at treeline elevations in the Brandywine area.
On Friday, a few human triggered avalanches up to size 2.5 were reported. A size 1.5 and a size 2.5 were triggered on southwest facing slopes between 1900 and 2000 m. These likely failed on the buried persistent weak layers.
Snowpack Summary
A thin sun crust has formed on solar aspects and the surface is wind affected in most exposed terrain. Last week's storms buried a weak layer composed of soft facets, surface hoar, and/or crust 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
TUESDAY: Clouds clearing in the morning and then sunny in the afternoon, light west wind, freezing level rising to around 1000 m.
WEDNESDAY: Sunny, light wind, freezing level rising to around 1300 m.
THURSDAY: Flurries increasing throughout the day with 5-10 cm of snow by the afternoon, moderate southwest wind, freezing level rising to around 1200 m.
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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.