Avalanche Forecast

Moderate -

Light snow is expected Tuesday overnight with the south of the region potentially receiving another 10-20 cm. A mix of sun and cloud is expected on Wednesday with the potential for isolated snow flurries. Alpine wind is forecast to be moderate to strong from the southwest and treeline temperatures are expected to be around -8C. Similar conditions are expected for Thursday with a mix of sun and cloud, isolated snow flurries, moderate alpine wind from the southwest, and treeline temperatures around -8C. A storm system is currently forecast to arrive Thursday evening and bring up to 30 cm of new snow by midday Friday. Alpine wind should be strong from the southwest during the storm and treeline temperatures are forecast to reach around -4C.

On Monday, explosives triggered three size 2.5 slab avalanches in the Duffey area which released on late-February sun crust down 40-50 cm. These were on southeast through southwest aspects at 2000-2200 m elevation. Extensive whumphing was also reported in the north of the region. On Sunday, a natural size 2 avalanche was observed on a southerly aspect in the Duffey area. A MIN post from Sunday describes a snowmobile triggered avalanche in the Coquihalla on Sunday. On Saturday, natural avalanches were reported up to size 2.5 from the north of the region and up to size 4 in the Coquihalla area which were failing on facets above a crust. On Wednesday, large persistent slab avalanches remain a serious concern with the snow from the past week releasing on the February weak layers. It may still be possible for a person to directly trigger a persistent slab or a smaller avalanche could step down. Moderate to strong southwest wind Tuesday overnight may develop new wind slabs in immediately leeward terrain features which may be touchy. Old lingering wind slabs and cornices may also still be reactive.

Another 10-15 cm Monday overnight brings the typical storm accumulation in the past week to 50-70 cm in the north of the region and to over 1 m in the south of the region. Strong south and southwest wind during the storm redistributed much of this snow in wind-exposed terrain forming thick wind slabs. The new snow overlies the mid-February and late-February interfaces which may be close together in the snowpack. The late-February interface consists of wind affected surfaces in exposed terrain, sun crust on steep solar aspects, and facets and surface hoar in sheltered areas. The mid-February interface consists of a thick rain crust which extends to at least treeline, a sun crust on steep solar aspects, and in many places, a layer of facets overlying the crust. Recent observations suggest the late-February layer is most reactive in the north of region and the mid-February layer is most reactive in the south of the region. Below these layers, the mid and lower snowpack are generally well settled and strong.