Winter continues. Snow forecast for Thursday is expected to build new storm slabs.
Confidence
Moderate - Forecast snowfall amounts are uncertain
Weather Forecast
THURSDAY: 15-30 cm snow. Moderate to strong southerly winds. Freezing level near 1500 m.FRIDAY: Light snow. Light southerly winds. Freezing level near 1500 m.SATURDAY: Light to moderate snow. Light winds. Freezing level rising to 1750 m.Weather models disagree on the amount of snow expected this week.
Avalanche Summary
A handful of skier-triggered size 1 storm slabs were reported on Tuesday. The size and likelihood of storm slabs are expected to increase with Thursday's storm. Cornice fall remains a possibility. A cornice could tickle a deeply buried weak layer and trigger a surprisingly large avalanche.
Snowpack Summary
Forecast snow is expected to build new storm/wind slabs on Thursday. Cornices are reported to be large and fragile. New snow will overlie various old surfaces including existing storm slabs, melt freeze crusts on sunny aspects, scoured old hard wind slabs and dry snow.A weak layer consisting of surface hoar, facets or a sun crust buried in late March is now down about 60-80 cm. This is patchy in its distribution, but is mostly likely to be problematic on shady aspects between 1900m and 2250m. The mid and lower snowpack are strong and well settled.
Problems
Storm Slabs
Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.
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.