A warm storm will bring rain, snow, and a range of avalanche hazards on Monday. Be aware of hazards changing and increasing as you gain elevation.
Confidence
Moderate - Freezing levels are uncertain
Weather Forecast
Sunday night: Periods of snow bringing 20 cm of new snow to higher elevations. Rain below about 1000 metres. Moderate to strong southwest winds. Monday: Continuing snowfall with 30 cm accumulating at higher elevations. Rain below about 1300 metres. Moderate southwest winds. Freezing level rising to 1700 metres by afternoon. Alpine temperatures around 0. Tuesday: Flurries bringing 5 cm of new snow to alpine elevations and intensifying overnight. Rain below about 1400 metres. Light to moderate south winds increasing over the day. Freezing level to 1800 metres and rising overnight. Alpine temperatures around 0 to +1. Wednesday: Continuing flurries bringing up to 10 cm of new snow. Moderate to strong southwest wind. Freezing level dropping from 2000 metres to 700 metres over the day. Alpine temperatures around 0 to -1.
Avalanche Summary
No new avalanches have been reported, but it should be noted that stormy weather has been discouraging some backcountry travel and obscuring visibility into alpine terrain.Looking forward, expect a change in avalanche hazards as you transition to higher elevations. Thick, reactive storm slabs can be expected at higher elevations, which increases the need for awareness of overhead hazards. Heavy rain will increase danger from loose wet avalanches at lower elevations. Large persistent slab avalanches may also remain sensitive to human triggering or to smaller avalanches in isolated areas of the alpine.
Snowpack Summary
Up to 50 cm of new snow can be expected to accumulate into touchy storm slabs on the surface at higher elevations by Monday afternoon. Below the surface, last week's stormy weather brought 130-200 cm of recent snow to the South Coast mountains. Below all the recent storm snow, you'll find the late-February interface. This layer is composed of a sun crust on southerly aspects and surface hoar on shaded aspects. Our supportive surface crust is likely to prevent triggering this layer at treeline and below, but this interface may remain reactive at alpine elevations. Although triggering this layer may be unlikely, doing so would produce a very large and destructive avalanche. Substantial snowfall and warming in the forecast are two factors that may promote reactivity at this interface on Monday. Below this interface, the mid and lower snowpack appear to be well settled and strong.
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.
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.
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.