Wind slabs may be reactive to human triggering at upper elevations, especially where they sit above a crust.
Conditions can change quickly with rain or strong solar input destabilizing the snowpack. Be ready to adjust your plans and scale back your exposure to avalanche terrain
Wind slabs may exist in lee terrain features in the alpine and treeline, formed by recent snowfall and westerly winds. These wind slabs will be most reactive where they overlie a slick crust.
If the sun comes out on Friday, wet loose activity can be expected on steep solar aspects at all elevations.
Avoid avalanche terrain if the snowpack becomes wet and unsupportive to your weight. At lower elevations, a poor overnight crust recovery followed by above freezing temperatures and rain may cause wet slab and wet loose avalanches to continue on all aspects.
Friday: Mostly overcast skies with 5-10 cm of new snow. Ridgetop wind will be moderate from the West. Freezing levels will likely rise to 1500 m during the day and fall to the valley bottom overnight.
Saturday/ Sunday: Mostly cloudy with possible sunny breaks and convective flurries. Ridgetop wind is moderate from the southwest and freezing levels will remain 1500 m.
On Wednesday, the region saw another natural cycle of wet loose, dry loose, wind slabs up to size 2, and wet slabs up to size 3. Additional reports continue to trickle in with deep persistent slabs up to size 4 from Tuesday- primarily occurred on southern aspects.
On Monday and Tuesday, a widespread natural avalanche cycle occurred with storm/wind slabs up to size 3 on all aspects, with the most reactivity noted on south-facing aspects. Numerous wet loose and wet slab avalanches occurred at treeline and below (size 1-3). A few of the larger size 3 notable wet slab and deep persistent slab avalanches that were reported are suspected to have failed on the early December rain crust near the base of the snowpack.
5-15 cm of new snow overlies up to 20 cm of denser snow above 2000 m. This tapers rapidly at lower elevations. Below 2000 m on all aspects and to the mountain top on solar aspects, a crust can be found. Below the crust, the top 10-50 cm of the snowpack is moist. Moderate West wind combined with the recent snow has formed reactive wind slab on lee terrain features in the alpine and at treeline.
At lower elevations (below treeline) a thick and robust melt-freeze crust exists making the snowpack strong. If the crust breaks down and softens to moist and/or wet snow, the snowpack becomes weak.
Several older crust layers exist in the upper snowpack and were buried in mid-March and near the end of March. A deep one formed in December and exists approximately a metre off the ground. Reports have recently indicated that large slab avalanches have failed on some of these interfaces within the past few days following a rain and warming event. The most reactive slopes were south-facing. These layers may be dormant now until the next warm-up or increased load from wind, snow and/or rain.
