A Special Public Avalanche Warning has been issued for this region for February 24-27. Current conditions are very touchy and require extremely conservative decision making.
Weather Forecast
Friday: Light to moderate snow beginning in the morning - 5-10cm. The freezing level (FL) is near valley bottom. Ridge top winds should be moderate from the SW. Saturday: Continued moderate snowfall - an additional 10-15cm overnight and through the day. FL rising to 800m. Winds should ease to light from the west. Sunday: Unsettled conditions with convective flurries likely. FL drops to valley bottom. Winds are light and variable.
Avalanche Summary
A natural avalanche cycle occurred on Wednesday in most areas. Slab avalanches were reported up to Size 2.5 on all aspects and at all elevations. There were also several reports of skier triggered avalanches and remotely triggered avalanches up to Size 2.0, and a Size 2 snowmobile triggered avalanche near Blue River. The potential for triggering large avalanches will remain high throughout the forecast period.
Snowpack Summary
Wind slabs continue to grow in exposed terrain in response to moderate SW-NW winds. 30-60cm of storm snow has now settled into a cohesive slab and overlies the Feb. 9 weakness, which includes surface hoar and/or a crust. This surface hoar layer may be widespread in some areas, while others have reported it being confined to shady aspects at treeline and in the alpine. A melt-freeze crust can be found down 50-70cm on solar aspects at all elevations, and on all aspects below about 1600 metres. In some areas this melt-freeze crust has facets above or below it. The mid-pack is generally well settled. There is some concern that large loads like cornices may trigger the Jan. 20th facet layer. Some shallow snowpack areas may continue to have a weak layer of basal facets near the ground.
Problems
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.
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.