Regions
South Coast Inland.
On Wednesday, touchy storm slabs are expected in the high alpine. Extra caution is also required on all sun exposed slopes if the sun comes out in full force.
Weather Forecast
On Wednesday, unsettled conditions are expected with snow flurries and sunny breaks both possible. Alpine wind is expected to be moderate to strong from the southwest. Freezing levels are forecast to drop to around 1000 m Tuesday night and reach around 1500 m in the afternoon. The next pulse of precipitation is expected to arrive Wednesday overnight or Thursday morning. There is currently quite a lot of model disagreement regarding amounts with 5-25 mm possible between Thursday morning and Friday morning. Alpine wind is expected to be moderate from the southwest on Thursday with freezing levels around 1000 m. Friday is currently forecast to be mainly dry with the next storm system arriving Friday overnight or Saturday morning.
Avalanche Summary
On Monday, numerous loose wet avalanches up to size 2 were observed in the Coquihalla area. In the north of the region, three natural size 1.5-3 cornice releases were observed on north and northeast aspects. Also in the north, a skier triggered a size 1 storm slab in a loaded alpine feature and a skier triggered a size 1 persistent slab on an east aspect at 1800 m which released down 40 cm on the late February surface hoar layer. On Sunday, two size 1 cornice releases were observed in the north of the region, one failed naturally and the other was skier triggered. On Wednesday, stability is generally expected to improve as temperatures drop. However, if the sun comes out, it can quickly destabilize the snowpack on sun exposed slopes. In the high alpine, the recent storm snow is expected to remain touchy, especially in wind loaded terrain.
Snowpack Summary
On Tuesday, freezing levels reached at least 2100 m. As temperatures drop on Wednesday, a new surface crust is expected to be widespread and the snowpack is expected to gain considerable strength. In the north of the region, the February weak layers are now down 80-120 cm. The layer of buried surface hoar has recently produced a few persistent slab avalanches. The crust/facet layer appears to be gaining strength but may also still be reactive in isolated areas. In the Coquihalla area, the crust/facet layer is down well over 1 m and appears to have gone dormant.
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.