Avalanche Forecast

Moderate - Due to the number of field observations on Sunday

A ridge of high pressure off the coast will slowly move eastward on Monday and should be established over the interior by Tuesday. Mostly cloudy conditions and light scattered flurries (0-3 cm) are expected for Monday. Alpine winds are expected to be light from the northwest in the morning but may become moderate in the afternoon. Freezing levels are expected to be at or below valley bottom during the forecast period. A mix of sun and cloud is expected for Tuesday with light to moderate westerly winds in the alpine. Increasing cloudiness is expected for Wednesday in advance of a weak storm system that is currently forecast to arrive on Wednesday night.

On Saturday, two natural size 2.5 storm slab avalanches were reported on south-southeast aspects. A snowmobile triggered a size 1.5 persistent slab on a northeast aspect at 1900m which released on a layer of surface hoar. Several remotely triggered size 2-2.5 wind slab avalanches were reported to have been triggered from up to 100m away in the alpine and at treeline. Ski cutting produced several size 1 storm slabs with a thickness of 10-20cm which released on small convex features. On Friday, numerous natural storm slab avalanches up to size 2.5 were reported in the region. Three skier triggered avalanches were also reported. One was remotely triggered from 10m away on an east aspect at 2000m. This released down 70cm suggesting it failed on the early January surface hoar layer. A size 1.5 was reported on a west aspect at 1900m failing down 100cm on the early January layer. The third was a size 1.5 on a northeast aspect at 1800m failing down 40cm also on the early January layer. Recently formed storm slabs and a reactive persistent slab are both expected to remain sensitive to human-triggering on Monday.

Recent snowfall and strong winds created storm slabs in many places and wind slabs on features lee to the southerly winds. This new snow has also added load and stress to the already volatile persistent slab. The recently destructive layers of surface hoar from early-January are now typically down 70-120cm and remain reactive. These layers have the potential for wide propagations and remote triggering, and smaller avalanches have the potential to easily step-down to one of these layers. The mid and lower snowpack are generally strong and well settled below these layers. Snowpack depths are variable across the region and shallow snowpack areas may have weak facetted crystals near the ground.