Heavy snowfall and high wind are producing touchy storm slabs. Give the snowpack time to stabilize.
Confidence
Low - Intensity of incoming weather systems is uncertain
Weather Forecast
THURSDAY NIGHT: Snow, 20-30 cm. Moderate south wind with extreme gusts. Freezing level rising to 1800 m.FRIDAY: Heavy snow, 20-35 cm. Moderate to strong southwest wind with extreme gusts. Freezing level dropping to 1200 m.SATURDAY: Flurries, 8-15 cm snow. Light south wind gusting moderate. Freezing level 1100 m.SUNDAY: Flurries, 5-12 cm snow. Moderate southwest wind. Freezing level below 1000 m.
Avalanche Summary
On Thursday, storm slab avalanches to size 2 were failing with explosives and skier traffic. Through the day, rain falling to 1500 m triggered loose wet and wet slab avalanches. Prior to Wednesday, avalanche activity seems to have tapered off as temperatures cooled off over earlier in the week. On Sunday there were reports of a few explosives controlled size 1-1.5 storm and wind slabs. On Saturday reports indicated several explosives controlled size 2 storm and wind slabs in the alpine and treeline. Most of these avalanches were running on a layer of surface hoar buried around December 26.
Snowpack Summary
Heavy snowfall, rising freezing levels and extreme winds are setting up a widespread storm slab problem. Around 40-80 cm of new snow since Wednesday adds to 30-50 cm of snow from the past week. This new load potentially sits on a weak layer of feathery surface hoar at treeline elevations and on a crust below 1800 m.A weak layer of sugary facets and surface hoar lies around 150 to 200 cm deep in the snowpack. There have not been reports of avalanches on this layer for over a week. That being said, this layer may still exist in isolated areas around treeline in some parts of the region. The additional weight of the new snow could stress deeper weak layers too.
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.