Strong winds and increasing rain will make for less than ideal travel conditions on Friday. Loose wet avalanche activity may be especially pronounced on high north aspects.
Steady warm temperatures and light rain will promote loose wet avalanche activity in the storm snow from last weekend. High elevations that haven't yet seen a melt cycle are the most prone. Conditions will deteriorate over the day as rain increases.
Thursday night: Increasingly cloudy. Moderate to strong southwest winds. Freezing level remaining near 2700 metres.
Friday: Cloudy with scattered showers and a trace to 3 mm of rain accumulating, continuing overnight. Moderate to strong southwest winds, easing overnight. Alpine high temperatures around +5 with freezing levels to 2700 metres, dropping to 1800 overnight.
Saturday: Cloudy with easing wet flurries leaving a possible trace to 5 cm of wet new snow at higher elevations. Light east winds. Alpine high temperatures around -1 with freezing levels to 2000 metres.
Sunday: Sunny with cloudy periods. Light southeast winds. Alpine high temperatures around +2 with freezing levels to 2400 metres.
An observation from the Waterton Park area describes a very large (size 3) deep persistent slab having released with a cornice trigger at some time in the past week. This occurred on a wind loaded high (2500m) north aspect on Mt. Blackiston and initiated as a wind slab before 'stepping down' to weak faceted snow in the basal snowpack. This should be treated as a reminder of the potential for weak basal snowpack conditions persisting in high alpine terrain.
The following activity resulting from the recent storm occurred in the neighbouring Lizard Range:
On Sunday storm slabs were quite sensitive to human triggering to size 2 on north through east facing slopes in the alpine and down into treeline. A little further down into treeline the snowpack was well bonded to the old crust, check out this MIN report for more details.
A natural avalanche cycle occurred Saturday night, the highlights were storm slabs up to size 2 on northeast facing alpine terrain around 1700 m. A natural cornice failure was observed from a north facing ridgeline which subsequently triggered a size 2.5 storm slab involving the new snow. We received a great MIN report of a small storm slab from Saturday morning.
Recent sun and temperature crusts are likely to be found on the surface on solar aspects and below the alpine, having formed above the 10 to 20 cm of dense snow from the past weekend's storm. In most areas, this storm snow sits above a widespread supportive crust. By Friday evening, light rain is expected to create moist snow conditions on all aspects and elevations.
North facing alpine terrain may still hold a cold, dry, snowpack and as a result may see more pronounced loose wet activity as rain saturates it for the first time. High elevation north facing terrain also harbours a deeply buried layer of facets. Although unlikely, human triggering of persistent slabs on this layer may still be possible in rocky alpine terrain with shallow or variable snowpack depth.
Below treeline the snowpack has melted or is isothermal.
