A warm, wet, and windy storm is expected to result in natural avalanche activity by morning.
Confidence
Fair - Timing, track, or intensity of incoming weather system is uncertain on Sunday
Weather Forecast
Overnight and Sunday: Strong Southwest winds and heavy precipitation overnight and Sunday morning. Freezing levels around 1800 metres overnight falling in the afternoon to 1000 metres.Monday: Mostly cloudy with light Westerly winds, some flurries and freezing levels rising to 1300 metres during the afternoon.Tuesday: Overnight freezing down to valley bottoms. Clear in the morning with light Westerly winds. Chance of snow in the afternoon as moisture pushed North of the ridge may slide down into the region.
Avalanche Summary
Some natural, skier controlled, and remotely triggered storm slab avalanches have been reported releasing down 30-50 cm. Some of these avalanches have released on buried melt-freeze crusts on Southerly aspects. Expect natural avalanches to continue and to increase in size as the storm slab continues to develop.
Snowpack Summary
In general, about 30-50 cm of storm snow overlies small surface hoar crystals in sheltered areas, a sun crust on solar aspects and wind slabs in exposed terrain. Further snowfall, wind and warming will add to the reactivity and destructive potential of this developing storm slab. There is ongoing concern for a mix of weak surfaces which were buried on February 10th. This persistent interface lies up to a metre below the surface, and includes weak surface hoar, well developed facets and a mix of hard surfaces which remain widespread at all aspects and elevations. For the most part, the mid and lower snowpack are strong and well consolidated. Weak basal facets exist in some areas, but triggering has now become unlikely.
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.
Persistent Slabs
Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.