Another day of sun and warm temperatures will maintain very dangerous avalanche conditions on Wednesday. Travel in avalanche terrain is not recommended.
Weather Forecast
Tuesday night: Clear. Light west winds. Freezing levels rising to 3300 metres.Wednesday: Sunny. Light west winds. Alpine high temperatures around +9 with freezing levels to 3400 metres, dropping slightly overnight.Thursday: Sunny. Light southeast winds. Alpine high temperatures around +8 with freezing levels of 3200 metres, remaining steady overnight.Friday: Sunny. Light variable winds. Alpine high temperatures around +7 with freezing levels around 3000 metres, dropping overnight to 2300 metres by mid-morning Saturday.
Avalanche Summary
A report from Tuesday in the Elk Valley described numerous natural persistent slab releases reaching size 2 (large) on southeast aspects at around 2200 metres. Further to this activity, any sun-exposed snow became isothermal (slushy and lacking cohesion), and huge whumpfs that collapsed the basal snowpack were triggered during ski touring.A report from Sunday in the Window Mountain area described snowshoeing party choosing to turn back after avoiding a large loose wet avalanche that ran into below treeline terrain. This highlights the importance of considering overhead hazards being warmed by the sun and potentially inverted (warmer at higher elevations) temperatures.Given the above activity, loose wet avalanches remain a daily concern in steep, sun-exposed terrain (and in runout zones) while concern is increasing for deep basal snowpack weaknesses that have the potential to produce very large and destructive slab avalanches.
Snowpack Summary
Upper snowpack: Getting warm and moist during the day, likely forming weak crusts overnight that deteriorate during the day. On sunny aspects there may be buried crusts serving as sliding layers. On lee slopes there may be buried hard layers of wind effected snow (buried wind slabs).Mid pack: The mid-snowpack consists of sugary faceted grains (facets) and layers of harder wind effected snow. In isolated sheltered locations a thin surface hoar layer from mid-January is 50-80 cm deep. The surface hoar is most prominent in the Elk Valley between 1600 - 1900 m. Lower pack: The strength of the lower snowpack is increasingly in question in shallower areas where the February cold was able to penetrate and weaken basal layers. Warm temperatures are increasing the strain on basal weaknesses each day.Forecasting how many sunny days and warm nights it's going to take to wake up deeper layers is tough, but we can say with confidence that it's a good time to stand aside and let the mountains shed their coat. Stability will improve greatly when temperatures cool off.
Problems
Loose Wet
Loose Wet avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.
Deep Persistent Slabs
Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.