Confidence
Fair - Intensity of incoming weather systems is uncertain on Wednesday
Weather Forecast
Overview: A zonal pattern will continue to bring moisture to the Columbia Mountains, particularly for Wednesday and Thursday. Expect higher freezing levels and greater accumulations further south within the region.Wednesday: 10-15cm of snow falling late in the day and overnight / Moderate westerly winds / Freezing level rising from surface to about 800m with the arrival of the system Thursday: Light snowfall / Moderate westerly winds / Freezing level at about 1200mFriday: Overcast skies / Moderate northwest winds / Freezing level at about 1200m
Avalanche Summary
Numerous size 2-2.5 sled-triggered slab avalanches occurred in the Valemount area over the last week. The February 10th interface was the culprit in these events. At the time of publishing, no new avalanche activity had been reported.
Snowpack Summary
In general, about 15-25cm of storm snow overlies small surface hoar crystals in sheltered areas, a sun crust on solar aspects and wind slabs in exposed terrain. Initially, these new accumulations are expected to be reactive as wind slab in pockets of exposed terrain. Once the new slab develops, 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 up to a metre below the surface, and includes weak surface hoar, well developed facets and a mix of hard surfaces which remain widespread at all aspects and elevations. Although natural avalanche activity has tapered-off at this interface, destructive avalanches are still a very real concern with ongoing reports of rider-triggering and sudden snowpack test result results. For the most part, the mid and lower snowpack are strong and well consolidated. Weak basal facets exist in some areas, but triggering has now become unlikely.
Problems
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.
Wind Slabs
Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind 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.