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.
Fresh wind slabs may exist in leeward (N-NE-E) terrain features in the alpine and exposed treeline. These 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 convective flurries possibly bringing 5-20 cm. Ridgetop wind is moderate from the southwest and freezing levels will remain near 1500 m.
On Wednesday, the recent storm snow was easily reactive to skier triggering, especially where it sits above a crust. Reports showed numerous dry loose and wind/storm slab avalanches size 1-2.
On Tuesday in the north of the region, several size 1-2 natural wind slabs were observed in the alpine. Throughout the region, a widespread wet loose/wet slab and deep persistent slab avalanche cycle occurred at all elevations up to size 3. The most reactivity was noted on solar aspects.
Up to 20 cm of new snow overlies 10-20 cm of denser snow above 2000 m. A crust can be found below the new snow on all aspects below 2500 m. Below the crust, the top 10-30 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 deeper 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.
