An intense storm is hitting the Sea-to-Sky region on Wednesday afternoon and danger will increase throughout the day as storm snow accumulates.
Confidence
Moderate - Intensity of incoming weather systems is uncertain
Weather Forecast
TUESDAY NIGHT: Light snow starting overnight with accumulations of 5-10 cm by the morning, moderate wind from the southwest, freezing level around 700 m with alpine temperatures dropping to -5 C.WEDNESDAY: 15-25 cm of snow, strong wind from the southwest, freezing level climbing to 900 m, alpine high temperatures around -2 C.THURSDAY: 20-50 cm of snow with freezing level climbing to 1600 m and strong to extreme wind from the southwest.FRIDAY: Another 20 cm of snow as freezing level drops to 1000 m and moderate wind from the west.
Avalanche Summary
Avalanche activity seems to have tapered off as temperatures have cooled off over the past few days. 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. Some of these avalanches were running on a layer of surface hoar buried around December 26.Looking ahead, a widespread storm slab problem will develop with the incoming storm. The additional weight of the new snow could stress deeper weak layers too.
Snowpack Summary
Fresh storm slabs will start to form on Wednesday as a storm tracks across the region from the north. Wind loaded terrain will be the first to develop reactive slabs.30-50 cm of snow from the past week 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.
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.