New snow and wind continue to build reactive storm slabs at upper elevations. Loose wet avalanches will become increasingly likely as rain soaks the surface snow below 1400 m.
Storm slabs will continue to develop throughout the day where precipitation falls as snow. The new snow does not appear to be bonding well to underlying surfaces in many areas. Storm slabs are especially likely to be triggered in steep or convex terrain and in wind loaded areas.
Loose wet avalanches will become increasingly likely as rain soaks the surface snow below 1400 m.
Monday night: 10-15 cm new snow, moderate southwest wind, alpine temperature -1 C, freezing level 1500 m.
Tuesday: 5-10 cm new snow, moderate southwest wind, alpine temperature -1 C, freezing level 1400 m.
Wednesday: 15-25 cm new snow, wind easing to light south, alpine temperature -1 C, freezing level 1200-1500 m.
Thursday: Clearing, light northwest wind, alpine temperature -1 C, freezing level 1000-1500 m.
Storm slabs were touchy on Sunday! Skier and explosive control work produced size 1-2 avalanches, a number of them remotely or sympathetically triggered. This MIN report describes a remotely triggered size 1 on a convex roll in an open area below treeline.
By Monday, storm slabs were still reactive but less electric. A natural cycle up to size 2 was observed through limited visibility in the Whistler backcountry. Explosive control work produced mostly size 1s with a couple size 2 storm slabs. On the other side of the 99, a size 1 wet slab was observed sliding on the crust on an east aspect at 1500 m.
20-50 cm of wind affected, upside-down storm snow sits over a variety of surfaces including sun crusts on solar aspects, a thick rain crust in windswept terrain and facets in shady, sheltered terrain. The upper snowpack is moist or wet below 1400 m.
A crust/facet/surface hoar interface formed late-January is buried down 40-100 cm. This layer was most reactive between 1700 m and 2000 m. While this layer has been dormant in most of the region lately, large loads such as heavy snowfalls and cornice falls could wake it up and produce very large avalanches.
