Confidence
Fair - Due to variable snowpack conditions
Weather Forecast
Saturday night and Sunday: Ridge of high pressure continues to dominate for the whole period. No precipitation, mild temperatures, scattered clouds and valley clouds and strong Westerly winds in the alpine tapering off slightly on Sunday.Monday: Similar conditions with warmer temperatures and freezing level rising to 1200 m. Tuesday: Dry conditions persist, light SW winds and freezing level around 1000 m.
Avalanche Summary
A couple natural avalanches up to size 3 were observed in Roger’s Pass area as well as a remote skier triggered slab avalanche size 1.5 on a windloaded feature at top of treeline in the same area. Another natural slab avalanche size 1.5 was reported which would have run on a steep NE facing slope.
Snowpack Summary
A trace to 3 cm of new snow fell with Strong NW-SW winds. Recent and past strong NW-SW winds have left wind slabs in many areas, even at treeline. These are gaining strength with mild temperatures and as the amount of snow available for transport diminishes. Around 40-60 cm settled storm snow sits above surface hoar, a sun crust (on steep S to SW -facing slopes) and facets. Results on the surface hoar layer vary from sudden planar to resistant planar in the moderate to hard range. It appears to be more reactive in the Northern part of the region, especially in the 1900 to 1500 m. range. The distribution of these weaknesses is patchy, but where they exist, it may still be possible to trigger a large avalanche with the weight of a person or snowmobile. A strong mid-pack overlies a weak facet/crust layer near the base of the snowpack, which is generally considered inactive.
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.