South Rockies

Human triggering of large deep persistent slab avalanches remains possible; especially in rocky, alpine terrain with a shallow or highly variable snowpack depth.

Moderate - Due to the number of field observations

SATURDAY NIGHT: Cloudy with alpine flurries; 5-10 mm / Light, easterly winds / Alpine low -4 C / Freezing level 1800 m.SUNDAY: Cloudy with alpine flurries; 3-5 mm. / Light, easterly winds / Alpine high -2 C / Freezing level 1800 m.MONDAY: Mix of sun and cloud / Light to moderate, southwesterly winds / Alpine high 1 C / Freezing level 2100 m.TUESDAY: Cloudy with alpine flurries; 3-5 mm. / Moderate to strong, southwesterly winds / Alpine high 0 C / Freezing level 2000 m.

Natural avalanche activity will taper off with the cloudy skies and cooling temperatures. Concern remains for human triggering deep persistent slab avalanches; especially in rocky alpine terrain with a shallow or highly variable depth snowpack.On Thursday, there were numerous reports of skiers triggering what started as small loose wet avalanches and then gathered mass and entrained the entire snowpack to the ground running much further than expected, up to size 2. Check out this video from our South Rockies Field Team HERE.A report from our South Rockies Field Team on Tuesday in the Elk Valley described numerous natural persistent slab releases reaching size 2 (large) on southeast aspects at around 2200 m. Further to this activity, any sun-exposed snow became isothermal (slushy and cohesionless), and large whumpfs that collapsed the basal snowpack were triggered during ski touring. Check out their video HERE.

The prolonged warm spell has transitioned sun exposed slopes in the alpine and all aspects at treeline and below towards becoming isothermal (0 C throughout the snowpack). In these areas that have entered spring conditions, the avalanche hazard will fluctuate greatly depending on the strength of the overnight freeze and how quickly the snowpack is warmed up each day. Check out this guide to managing avalanche hazard during spring conditions HERE.In areas that remained more sheltered from the heat, like northerly aspects in the alpine, there may still be a dry snowpack with a well settled slab sitting on weak facets (sugary snow). Human triggering of persistent slabs on this layer may still be possible.Lower down in the snowpack, the base is composed of weak facets. Large deep persistent slab avalanches initiating on these facets is currently the primary concern for this region. They are most likely in rocky, alpine terrain where there is a shallow or highly variable snowpack depth. They would likely require a large trigger such as a cornice fall, snowmobile, or a group of people standing in the same spot.