Wind slabs are still lingering on north aspects in the alpine - the same terrain where the best skiing is likely to be found.
Weather Forecast
Saturday: Mainly cloudy with isolated flurries bringing up to 5 cm of new snow, beginning in the afternoon. Winds light to moderate from the southwest. Freezing level to 500 metres with alpine temperatures of -10. Sunday: A mix of sun and cloud with isolated flurries and a trace of new snow. Winds light from the northeast. Freezing level to 700 metres with alpine temperatures of -9. Monday: Cloudy with sunny periods and isolated flurries bringing a trace of new snow. Winds light from the west. Freezing level to 400 metres with alpine temperatures of -10.
Avalanche Summary
Reports of both natural and skier triggered wind slab avalanche activity in the region have tapered off, with small natural and skier triggered loose snow releases dominating Thursday's reports. A MIN report from Wednesday describes a rider involvement in a wind slab avalanche on Fissile Peak, highlighting our ongoing concerns for isolated wind slabs in alpine terrain. On Wednesday in the far north of the region, several wind slabs were observed to have run naturally up to Size 2.5 out of steep, leeward terrain. Recent strong southerly winds were identified as the trigger.
Snowpack Summary
Flurries over Thursday night deposited 1-5 cm of new snow on the surface. Moderate southwesterly winds accompanied the snowfall, making a small contribution to our upper elevation wind slab problem. Below our thin new snow accumulations, recent cool temperatures resulted in up to 5 mm surface hoar growth on the previous snow surface, as well as surface faceting. Sun crusts have also recently been reported to be forming on steep solar aspects. Below the new snow interface, roughly 20-40 cm of recent storm snow appears to be bonding well the widespread mid-February melt-freeze crust. This crust extends as high as 2200 m and is up to 15 cm thick at treeline. Below this crust the mid and lower snowpack are well settled and bonded.
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.