High elevations hold dry snow seeing warming for the first time. Watch for signs of instability, moist surface snow and new natural avalanches.
Avoid large unsupported slopes, deeply buried weak layers remain a concern.
Pockets of wind affected snow from the strong south-southwest winds may still be reactive to a human trigger. Take care around wind loaded ridgelines and cross loaded features mid slope.
A deeply buried weak layer of sugary facets over a crust produced large naturally triggered avalanches during the last storm with rising freezing levels. Small storm avalanches may step down to these deeper instabilities producing large and destructive avalanches.
This layer is most likely to be triggered from thin or variable depth snowpack areas such as wind affected features, ridge crests, and near rocky outcroppings.
Expect loose wet avalanches to still be possible to trigger, even as the weather improves. Greatest concern is areas of dry snow at higher elevations that will see warm temperatures and sunshine for the first time.
Watch for terrain that holds heavy and wet surface snow.
Freezing levels continue to change rapidly in the wake of the storm, reaching peak elevations on Friday and likely again on Sunday.
THURSDAY NIGHT: Partly cloudy with no precipitation expected. Freezing levels rise to 2500 m with light westerly winds.
FRIDAY: A mix of sun and cloud with isolated flurries expected. Winds return to strong southwest. Freezing levels drop from 2500 m to 1500 m in the morning.
SATURDAY: Cloudy with isolated flurries. Freezing levels stay below 1500 m. Strong westerly winds.
SUNDAY: Mostly cloudy with light snow. Increasing westerly winds. Freezing levels around 1500 m.
Heavy precipitation and warm temperatures produced widespread natural avalanche cycles at all elevations. At treeline and below saw a loose wet avalanche cycle to size 3 on all aspects, during the most intense rain and warming. Upper treeline and alpine terrain produced a storm slab cycle to size 3 in most areas.
A size 4 avalanche was naturally triggered near Harrison Lake. This was thought to have started as a cornice fall which triggered a storm slab and stepped down to a deeper weak layer, up to 3 m deep in places.
Heavy precipitation over the last week has created a variety of surface snow conditions. Strong southwest winds have created pockets of dry snow at alpine elevations on north through east facing slopes. Precipitation fell as wet snow or rain below 2200m, creating saturated snow that is forming a melt freeze crust with moist snow below.
A crust that formed prior to the rain was observed up to 2000m. This is now buried up to 30 cm deep and may be breaking down at lower elevations where rain had a greater impact.
Two buried weak layers of sugary, faceted grains sit in the middle and lower snowpack, at 100cm deep and 150-250 cm deep. The deeper layer was formed by heavy rain followed by a cold spell in early December. It is most prominent between 1700 and 2100 m. Avalanches on this layer are large, but sporadic and isolated. The most likely place to trigger it would be in thin, rocky snowpack areas. The lower snowpack is well-settled and strong.
