Regions
South Coast Inland.
A cooling trend will eventually help stabilize the snowpack. Continually reassess conditions as you travel into avalanche terrain and be aware of the potential for deeper weaknesses in the snowpack.
Confidence
Moderate - Due to the number of field observations
Weather Forecast
SUNDAY: Clearing skies following the storm, light to moderate west winds, alpine temperatures drop to around -10 C.MONDAY: Mix of sun and cloud, light winds, alpine temperature around -7 C.TUESDAY: Cloudy with sunny periods and isolated flurries, light winds, freezing level climbs to 1500 m with alpine temperatures around -3 C.
Avalanche Summary
On Friday, a large cornice fall missed a group of skiers on a north aspect in the Duffey area (see MIN report for details). The previous day another skier remotely triggered a size 1.5 avalanche on a nearby south aspect at treeline. On Saturday, explosive control produced a few size 2-2.5 storm slabs and a few natural storm slabs were reported in the northern part of the region.On Sunday, storm slabs may remain reactive in human triggers. In northern parts of the region, the deeper February weak layers continue to present a low probability / high consequence scenario.
Snowpack Summary
Storm snow amounts on Saturday totalled roughly 40 cm around Coquihalla and Allison Pass and 30 cm around Duffey Lakes. Freezing levels reached roughly 1400 m, resulting in rain and/or wet snow at lower elevations. Thicker wind slabs and large cornices likely exist in alpine terrain. The storm snow sits above a widespread rain crust up to about 2100 m, but the snow will likely form a good bond to this crust. In the north of the region, the February weak layers are 80-120 cm deep and include a buried surface hoar layer that recently produced a few persistent slab avalanches and a crust/facet layer that appears to be gaining strength. In the southern parts of the region, the lower snowpack is generally stable.
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.