New snow and strong winds will rapidly raise avalanche danger with the onset of a winter storm on Friday.
Confidence
Poor - Timing, track, or intensity of incoming weather is uncertain
Weather Forecast
Synopsis: An intense storm will impact the region on Friday afternoon/evening, then briefly clearing on Saturday before another storm hits later on Sunday.Friday: 10-15 cm new snow is expected, starting in the afternoon. Strong southwesterly winds becoming gusty northwesterly to 90 km/h at ridgetop. Freezing level 1600 m.Saturday: Light snow in the morning, dry in the afternoon. Winds becoming light northwesterly. Freezing level 1000 m.
Avalanche Summary
Small soft slab avalanche could be skier-triggered on Thursday. Loose snow avalanches have also been reported in the recent new snow.
Snowpack Summary
Southeastern parts of the region have seen 30-60cm new snow in the last few days, while western areas have seen more like 10-20 cm. Mostly this snow has been light and overlies old wind slabs on higher north and east facing terrain and sun crusts on solar aspects. There may be localized areas where the wind has blown the new snow into isolated wind slabs in exposed areas. A surface hoar/facet/sun crust layer from mid February (12th) may be buried in the top 35 cm or so, but has not been widely reported from this region. Mid and lower snowpack layers are generally well settled and stable.
Problems
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.