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: Partly cloudy, light to moderate SW wind, freezing level low around 1500 m/high around 2000 m.
Thursday: Mainly sunny, moderate to strong SW wind, freezing level high near 2500 m in the north, 3000 m in the south.
Thursday night: Precipitation 5-10 mm, strong SW wind, freezing level 2500 m dropping to around 1300 m.
Friday: Snowfall 5-10 cm in the morning, a chance of sunny breaks in the afternoon, moderate to strong SW wind, freezing level high around 1600 m.
Saturday: Mainly cloudy with sunny breaks and a chance of flurries, light to moderate W wind, freezing level high around 1000 m.
An early report from Wednesday includes three explosive-triggered size 1.5-2 wind slabs in the north of the region on northwest and north aspects at 2200 m.
On Tuesday, a skier remotely triggered two size 1 storm slabs from 2 m away on a northeast aspect at 2000 m in the north of the region. These were 30 cm thick and failed on the underlying melt-freeze crust. In the Coquihalla area, a few natural size 1 storm slabs were reported.
Several older avalanches were also reported on Tuesday which had occurred during the storm including evidence of a natural cycle up to size 2.5 in the north of the region and a few natural cornice releases which triggered size 2 slabs failing on the underlying crust.
The recent storm produced around 30-50 cm of new snow in the north of the region and around 40-70 cm in the south of the region. 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 during the storm has redistributed the new storm snow in exposed, high elevation terrain forming wind slabs and developing large cornices. Windward slopes have been scoured down to the crust and the alpine snow surface is expected to be highly variable.
The middle and lower snowpack are generally strong and well bonded.
