Confidence
Fair - Timing, track, or intensity of incoming weather system is uncertain
Weather Forecast
Overview: A series of disturbances are embedded in a west/southwesterly flow which will bring continued snowfall to the region. There is some model disagreement in the track and timing of the systems; however, southern parts of the region are generally expected to see the highest accumulations.Monday night: Up to 20cm of snow / Strong southwest winds / Freezing level at surfaceTuesday: Light snowfall / Moderate to strong westerly winds / Freezing level at surfaceWednesday: 10-20cm of snow / Light ridgetop winds / Freezing level at about 500mThursday: Light flurries / Moderate to strong southwest winds / Freezing level at about 1000m
Avalanche Summary
Over the weekend 2 size 2 skier-triggered avalanches (1 was remotely triggered from 25m) occurred in the Monashees. The February 10th interface was the culprit in these events. A few remotely triggered size 1 hard wind slabs were also noted over the weekend in exposed lee terrain. They formed in response to strong winds and redistribution of surface snow on Friday night. I would expect fairly widespread storm slab avalanche activity with ongoing snowfall and wind.
Snowpack Summary
In many areas over 40cm of storm snow overlies surface hoar in sheltered areas, a sun crust on solar aspects and wind slabs in exposed terrain. Initially, these new accumulations are expected to react as a wind slab in exposed terrain. As the new slab deepens and gains cohesion by wind and warming, more widespread storm slab activity can be anticipated.There is ongoing concern for a mix of weak surfaces which were buried on February 10th. This persistent interface lies between 80 and 130cm below the surface, and includes surface hoar, well developed facets and a mix of hard surfaces which remain widespread at all aspects and elevations. Although avalanche activity at this interface has generally tapered-off, large destructive avalanches are still a very real concern with recent reports of remote-triggering, "whumpfing" and sudden snowpack test results. For the most part, the mid and lower snowpack are strong and well consolidated.
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.