Major warming with periods of strong spring sun are expected to create dangerous avalanche conditions on Thursday and a natural avalanche cycle is possible in the afternoon.
Check out this new blog post for examples of avalanche activity we may see Thursday.
Cornices have grown large during the recent storm and are expected to become weak during Thursday's warming, especially with extended exposure to the sun. Falling cornices are a likely trigger for slab avalanches on the slopes below.
The recent storm snow is expected to settle rapidly with major warming and periods of sun on Thursday. This may result in the formation of a more cohesive and reactive storm slab, and natural storm slab avalanches are possible in the afternoon.
Loose wet avalanches are likely on steep slopes during Thursday's warming, especially with extended periods of sun exposure.
A major warming event is forecast for Thursday with freezing levels climbing to at least 2500 m. A storm system is expected to arrive Thursday night which will replace the warm air and linger into Friday morning.
Wednesday Night: Mainly cloudy, light to moderate SW wind, freezing level climbing to around 1800 m.
Thursday: Mainly cloudy in the morning, a mix of sun and cloud in the afternoon, moderate to strong SW wind, freezing level high near 2700 m.
Thursday night: Precipitation 20-50 mm, strong SW wind, freezing level 2000 m dropping to around 1200 m.
Friday: Snowfall 5-10 cm in the morning, sunny breaks in the afternoon, moderate SW wind, freezing level high around 1500 m.
Saturday: Mainly cloudy with sunny breaks, light to moderate W wind, freezing level high around 800 m.
On Tuesday, skiers triggered a few avalanches including a size 1.5 storm slab on a steep west aspect at 2000 m, a size 1 avalanche in a steep north aspect couloir at 2150 m, and a remotely triggered size 2 storm slab from 2 m away. A ski cut triggered a size 1.5 cornice release on a northwest aspect at 1900 m. Explosives triggered numerous size 1-2.5 storm slabs and cornices up to size 2.5. The storm slabs were typically up to around 60 cm thick and many were sliding on the underlying melt-freeze crust. Several of the cornice releases triggered slabs on the slopes below.
A variety of older avalanches were also reported on Tuesday which had occurred during the storm including evidence of a natural size 2 storm slab cycle. A natural cornice release was observed which triggered a size 3 storm slab and a few other natural cornice releases which triggered size 2 storm slabs.
The recent storm produced 60-80 cm of new snow in the Whistler area. This storm snow has buried a firm crust which extends to mountain top on solar aspects and to around 2200 m on northerly aspects. This crust has been the sliding surface for many of the recent storm slab avalanches. Strong to extreme southwest wind has redistributed the new storm snow in exposed, high elevation terrain forming wind slabs up to 150 cm thick and developing large cornices. Windward slopes have been scoured down to the crust and the alpine snow surface is expected to be highly variable. A new sun crust was reported to be forming on the snow surface on Tuesday.
The middle and lower snowpack are generally strong and well bonded.
