Storm snow may remain sensitive to human and even natural triggering Monday as the new snow feels the strong March sun for the first time. The new snow needs a bit of time to stabilize before we start gunning for the bigger objectives.
20-30 cm of new snow has settled into storm slabs that are unlikely to be bonding well with the previous snow surface. Warming temperatures and clear skies Monday may allow the new snow to remain sensitive to human triggering. Beware of wet loose avalanches releasing naturally on steep slopes exposed to the sun too.
Weak snow at the bottom of the snowpack hasn't gone away. Evidence of deep persistent slab avalanches has been focused in the Sparwood-Elkford area over the past month. Human triggering is most likely around steep rocky terrain features, or anywhere the snowpack is thin and weak. Cornices have grown large and loom over many ridge lines, a failing cornice could initiate a deep persistent slab when it impacts the slope below.
Enjoy the sun Monday.
SUNDAY NIGHT: Freezing level at valley bottom, light west/southwest wind, trace of snow possible.
MONDAY: Clear skies, freezing level rising to about 1500 m, light southwest wind, no significant precipitation expected.
TUESDAY: Clear skies in the morning becoming cloudy after lunch, freezing level rising to about 1500 m, moderate to strong southwest wind, no significant precipitation expected during the day, potential for 3 to 6 cm of snow at upper elevation Tuesday night.
WEDNESDAY: Broken cloud cover, freezing level holding at 1500 m, light to moderate west/northwest wind, trace of snow possible.
In the neighbouring Lizard Range on Sunday loose dry and soft slab avalanches were sensitive to human triggering and control work to size 1.5. Avalanches there were 10 to 20 cm in depth, running fast and far. Similar conditions are expected to exist in the South Rockies & the storm snow may remain sensitive to human triggering Monday.
The Friday/Saturday storm produced 20 to 30 cm of new snow which buried heavily wind affected surfaces in exposed areas as well as a sun crust that may be present all the way to ridge top on solar aspects. Temperature crusts extend up to about 1900 m on other aspects. This storm snow has not yet bonded to the old surfaces and is touchy.
A thick rain crust currently sits 40-80 cm below the surface and can be found up to 2100 m. Avalanche activity was last observed at the faceting interface between this crust and overlying snow on February 17. The mid-pack is well settled and strong, but the base of the snowpack contains basal facets that are most prominent in shallow rocky start zones.
