Conditions are expected to change during the day. The loose wet avalanche cycle should taper off with cooling temperatures, but glide slabs and persistent slabs may continue to fail.
Confidence
Moderate - Freezing levels are uncertain on Monday
Weather Forecast
A front passing through on Monday is expected to bring cloud, light precipitation and moderate to strong SW winds, with the freezing level falling from around 2700 m to 1800 m. Cloud and a few snow showers may linger on Tuesday morning, before a ridge brings dry and very warm weather again.
Avalanche Summary
A cycle of large natural avalanches has been reported from the north Elk Valley, which occurred on Friday and Saturday. At least one of these appears to be a persistent slab, and all were likely to have been triggered by warming. A size 2.5 storm slab also released in steep rocky terrain in the south-east on Friday. Although temperatures are expected to cool on Monday night, they shoot right back up after that. The cycle may continue...
Snowpack Summary
Large cornices overhang alpine slopes. Glide cracks have opened up on several slopes and herald more glide avalanches to come. Recent storm snow (which was deepest in the south-east) has settled with continued warm temperatures. Crusts which have been forming at the surface by night have been breaking down quickly by day and low elevation and thin snowpack areas have become isothermal. Deeply buried weak layers in the mid snowpack and near the ground appear to have woken up in some areas with prolonged warming (see avalanche discussion).
Problems
Cornices
Cornice Fall is the release of an overhanging mass of snow that forms as the wind moves snow over a sharp terrain feature, such as a ridge, and deposits snow on the downwind (leeward) side. Cornices range in size from small wind drifts of soft snow to large overhangs of hard snow that are 30 feet (10 meters) or taller. They can break off the terrain suddenly and pull back onto the ridge top and catch people by surprise even on the flat ground above the slope. Even small cornices can have enough mass to be destructive and deadly. Cornice Fall can entrain loose surface snow or trigger slab avalanches.
Persistent Slabs
Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.