A capping crust may help to hold deep persistent slab problems at bay on Tuesday. Expect increased danger at alpine elevations and be aware of the potential consequences of releasing a heavy trigger such as a wind slab or cornice.
Summary
Confidence
Moderate -
Weather Forecast
Tuesday: Cloudy with scattered flurries and up to 5 cm of new snow, light rain climbing to about 1600 metres. Light south winds. Freezing level rising to 2000 metres with alpine temperatures around 0. Wednesday: Mainly cloudy with isolated flurries and a trace of new snow, light rain below about 1600 metres. Strong southwest winds. Freezing level to 2000 metres with alpine temperatures around 0. Thursday: A mix of sun and cloud with isolated flurries and a trace of new snow, light rain below about 1400 metres. Moderate to strong southwest winds. Freezing level to 1800 metres with alpine temperatures around -4.
Avalanche Summary
No new avalanches were reported on Sunday. Reports from Saturday included two explosives triggered Size 2 wind slabs south of Crowsnest Pass. These occurred on northeast to southeast aspects in alpine terrain and featured crown fracture depths of 20-80 cm.A report from Friday in the Crowsnest area showed a natural Size 3.5 deep persistent slab that began as a ridgetop wind slab release before stepping down to ground as it descended its track. Another explosives triggered Size 3.5 deep persistent slab was reported north of Sparwood. The resulting debris pile appeared to be roughly 10 metres high.Looking forward, recently formed wind slabs at alpine elevations may remain reactive to natural and human triggering on Tuesday, especially if they see rainfall. While recent strong crust recovery has been tempering the likelihood of persistent slab activity, another rise in freezing levels and forecast rain may prompt renewed persistent slab activity.
Snowpack Summary
Light recent snow accumulations have been redistributed into wind slabs in alpine terrain while rain recently soaked the snowpack at treeline and below. Lower temperatures have since formed a crust at the rain soaked surface, which will tend to deteriorate with daytime warming. Below the new snow and crust, regular snowfall throughout early March saw roughly 50-90 cm of snow accumulate above the crust and facet interfaces from mid and late February. In some areas this storm snow may have a poor bond to these interfaces. Aside from that uncertainty, the mid-pack in the region is generally strong. With that said, the bottom third of the snowpack is composed of weak sugary facets roughly 1-1.5 metres deep. The potential for full-depth avalanches over this basal weakness remains a real concern, with potential triggers including wind slab or cornice releases as well as forecast warming and rain.
cgarritty,
Avalanche Canada
