We are back into avalanche season. Touchy wind slabs are forming in the alpine and in exposed tree-line features.
Weather Forecast
We'll see isolated flurries today, with ridge top winds gusting to moderate from the west. Freezing levels remain below 800m. Friday will bring mixed sun/cloud with little in the way of precipitation. Winds remain light to moderate with freezing levels in the valley bottom. Light to moderate snowfall is forecasted for the weekend.
Snowpack Summary
In the alpine up to 35 cm of new snow buries the January 4th interface. This interface is surface hoar in protected areas, sun crust on steep S - SW aspects and loose facets at tree-line and below. Winds overnight have begun gusting to moderate values from the SW, creating a more reactive slab.
Avalanche Summary
Yes, we have something to talk about here! Numerous slab avalanches from N and S aspects (Mt Macdonald and Mt Tupper) were observed yesterday. Size ranged from 1.5 to 3.5, with steep, rocky start zones, and most avalanches running close to valley bottom. A few loose and slab avalanches to size 2 were observed west of Rogers Pass.
Confidence
Wind effect is extremely variable
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.
Loose Dry
Loose Dry avalanches are the release of dry unconsolidated snow and typically occur within layers of soft snow near the surface of the snowpack. These avalanches start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-dry avalanches include point-release avalanches or sluffs.