Regions
Northwest Coastal.
Warm, wet, and windy conditions are expected to increase the avalanche danger to HIGH.
Confidence
Moderate - Forecast snowfall amounts are uncertain on Saturday
Weather Forecast
Overnight: 10-20 cm of new snow above 600 metres combined with moderate gusty southwest winds. Saturday: 10-15 cm during the day with moderate westerly winds and daytime freezing up to 1100 metres. Sunday: Light west winds with flurries or periods of light snow and freezing levels around 1000 metres. Monday: Broken skies with a chance of clearing in the afternoon.
Avalanche Summary
One natural ice fall and one natural cornice fall size 3.0 were reported from the Bear Pass area on Thursday. Numerous natural storm slabs up to size 2.0 were reported on Wednesday. I suspect that new storm slabs will develop overnight due to the forecast new snow and wind.
Snowpack Summary
Storm slabs continue to develop in the alpine and at treeline. Warm daytime temperatures have created moist snow at treeline and wet snow below treeline. The February 21st persistent weak layer continues to be a concern for triggering large avalanches. This combination of crust and weak facets is now down 100-150 cm, and may be triggered by light additional loads in shallow weak spots adjacent to large terrain features. The snow below treeline may become weak and release as loose wet avalanches or wet slabs in steep unsupported terrain features.
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.
Loose Wet
Loose Wet avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.