Intense solar radiation may cause a spike in avalanche activity on sun-exposed slopes.
Confidence
Fair - Timing, track, or intensity of incoming weather is uncertain on Friday
Weather Forecast
Wednesday: Mostly clear with light winds and freezing levels rising to around 1200m. Thursday: Increasing high clouds throughout the day with light winds and freezing levels as high as 2500m for the southernmost part of the region. Friday: Mostly cloudy with snow increasing in the afternoon. Freezing levels around 1000m and moderate southwesterly winds.
Avalanche Summary
Reports from Monday include numerous Size 1-2 explosive-triggered and slope-cut soft wind slab avalanches. One of the larger slope-cuts stepped down 60cm to an old buried wind slab, while another failed on a crust buried last week and propagated onto 15 degree terrain. A brief period of strong solar radiation in the morning caused a couple of Size 3 loose snow avalanches on the Squamish-Cheakamus divide. These started off as surface sluffs and eventually entrained all of the recent storm snow on the entire slope and ran full path.
Snowpack Summary
Around 50-60cm of recent low density storm snow and/or weak wind slabs are bonding poorly to a variety of old snow surfaces, including crusts and wind slabs, from last week. Recent winds and precipitation patterns have created a highly variable slab depth with ability to propagate in low angled terrain and a structure conducive to step-down avalanches. The top 10cm or so is becoming moist during the day with sun exposure, and there is still a lot of snow available for reverse-loading if outflow winds pick up.
Problems
Wind Slabs
Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.
Storm Slabs
Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.