A variety of weak layers have been preserved within and below our recent storm snow. We're still managing a midwinter snowpack that requires thoughtful terrain selection.
Summary
Confidence
High -
Weather Forecast
Tuesday night: Scattered flurries and a trace to 5 cm of new snow. Light to moderate southwest winds.Wednesday: Mainly cloudy with continuing isolated flurries and a trace of new snow. Light to moderate southwest winds. Freezing level to 1500 metres with alpine high temperatures around -5.Thursday: Cloudy with light flurries beginning in the evening and continuing overnight. Light southeast winds. Freezing level to 1500 metres with alpine high temperatures around -5Friday: Cloudy with continuing isolated flurries and a trace of new snow. Light southeast winds. Freezing level to 1600 metres with alpine high temperatures around -3.
Avalanche Summary
Reports from Monday include several more observations of both new and recent storm slab avalanches from a variety of triggers ranging from size 1-2. Fracture depths of 20-40 cm indicate some of the shallower weak layers identified in our snowpack discussion as failure planes. More sporadic reactivity at the deeper mid-March layer was observed in adjacent regions. Numerous small (size 1-1.5) and reportedly hard wind slabs were also triggered on various aspects with both explosives and ski cutting.Saturday's reports included numerous observations of storm slabs releasing naturally as well as with skier traffic and explosives control. Sizes ranged from 2-3, with crown fracture depths varying from 30-100 cm. This activity occurred on all aspects but was focused at alpine elevations and this problem is now being identified as a 'persistent slab'. Wind slab releases made up a large number of observations, noted predominantly on southeast aspects.Widespread avalanche activity occurred in the top 30 cm of new snow on Friday. Numerous size 1 avalanches were reported, with the most reactive conditions on wind-affected slopes at treeline on north and east aspects.
Snowpack Summary
A variable 5-20 cm of new snow over Sunday night brought storm snow totals from the past week to a wide-ranging 50-90 cm, with amounts that taper with elevation. The snowfall was initially accompanied by strong south winds and then followed by strong north winds, so a mix of old and stubborn and newer, more reactive wind slabs can now likely be found on a range of aspects at higher elevations.Below the wind-affected surface, a few regionally variable weak layers exist within the depth of the recent storm snow, formed during breaks in storms that allowed for the formation of sun crusts on sun exposed slopes as well as surface hoar on shaded aspects. These shallower layers (20-50 cm deep) remain a concern, as does the similar mid-March persistent weak layer, now buried up to a metre deep. The reactivity of these layers appears to decrease with depth, however the mid-March layer still features in daily reports and the potential for deep 'step down' types of releases can't yet be dismissed.Deeper persistent weak layers from January and December are still being reported by professional observers, but are generally considered dormant.
cgarritty,
Avalanche Canada
