Avalanche danger may spike on slopes that are getting warmed by sunshine or warm temperatures. Be alert for changing conditions throughout the day.
Confidence
Fair - Timing or intensity of solar radiation is uncertain on Tuesday
Weather Forecast
Tuesday: No snow. Partly cloudy. Light S winds. Alpine temperature near -2. Wednesday: Light snow. Light S winds. Alpine temperature near -1. Thursday: Light snow. Light S winds. Alpine temperature near 0.
Avalanche Summary
There was a report of a skier triggered size 2 slab avalanche on Saturday from a rocky south-facing alpine slope, in an area just north of Whistler. A few natural cornice falls triggered thin slabs up to size 2 on the slope below. Solar warming also triggered a few small loose wet avalanches on steep sunny slopes. Skiers triggered small slabs on steep convex rolls on Sunday.
Snowpack Summary
Wind slabs, which recently formed on a widespread basis, have become harder to trigger. On sun-baked and low elevation slopes, a melt-freeze cycle is in play at the snow surface, leaving a crust behind during overnight cooling, which breaks down by day. The upper snowpack structure is highly variable. On sunny aspects (and all aspects at low elevations), a melt-freeze crust is now buried about 30 cm deep, while on high elevation shady aspects, 50-100 cm snow overlies an older melt-freeze crust. Bonding at both of these crust interfaces appears to be improving. Large cornices are looming over some slopes. Mid and lower snowpack layers are well bonded.
Problems
Cornices
Cornice Fall is the release of an overhanging mass of snow that forms as the wind moves snow over a sharp terrain feature, such as a ridge, and deposits snow on the downwind (leeward) side. Cornices range in size from small wind drifts of soft snow to large overhangs of hard snow that are 30 feet (10 meters) or taller. They can break off the terrain suddenly and pull back onto the ridge top and catch people by surprise even on the flat ground above the slope. Even small cornices can have enough mass to be destructive and deadly. Cornice Fall can entrain loose surface snow or trigger slab avalanches.
Loose Wet
Loose Wet avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.