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 afternoon.
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 around 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, moderate to strong SW wind, freezing level climbing to around 1800 m.
Thursday: Mainly cloudy in the morning, sunny breaks in the afternoon, strong to extreme SW wind, freezing level high around 2500 m.
Thursday night: Precipitation 5-10 mm, strong to extreme 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 NW wind, freezing level high around 1300 m.
Saturday: A mix of sun and cloud in the morning, light snowfall in the afternoon, moderate to strong NW wind, freezing level high around 800 m.
On Tuesday, the Avalanche Canada field team observed a size 1.5 storm slab on a north aspect which was expected to have occurred near the end of the storm on Monday. This MIN report describes numerous size 1-2 storm slabs which had occurred during the storm, primarily on northwest through east aspects resulting from wind loading.
Observations are very limited this time of year. If you are getting out in the backcountry, please consider sharing your observations to the Mountain Information Network.
The recent storm is estimated to have produced 60-100 cm of new snow. This storm snow has buried a widespread, supportive melt-freeze crust. Recent observations suggest the new snow is relatively well bonded to this underlying crust but it still has the potential to be a sliding surface for storm slab avalanches during the upcoming warming event. Strong to extreme southwest wind during the storm had redistributed this storm snow in exposed, high elevation terrain forming touchy wind slabs and building large cornices.
Reports from Tuesday suggest the recent storm snow remains mostly unconsolidated in sheltered terrain. With sun on Wednesday and major warming on Thursday, the storm snow is expected to settle rapidly and form a more cohesive slab which is expected to increase the avalanche danger in the short term.
The middle and lower snowpack are generally strong and well bonded.
