Heads Up. Conditions are changing rapidly. Forecaster confidence is low, as forecast snowfall totals vary widely. Avalanche danger will vary accordingly, and so should your plans.
Weather Forecast
Moist, mild Pacific air collides with a cold Arctic High. Forecasts predict anywhere from 40-140cm of snowfall by Monday evening. Alpine winds are mainly moderate SW (Strong on Sunday AM). Below Treeline, a cold Upslope flow with light NE windsprevails (except for Moderate SW winds Sunday AM), causing a temperature inversion. Monday looks frigid.
Snowpack Summary
Substantial new snowfall from Friday to Monday falls on wind-hardened snow, or pockets of very hard wind slab in open areas, 5-15cm thick. In some places this overlies a thin weak layer, seeming especially pronounced at the transition from sheltered to open terrain. The lower snowpack facets have produced isolated Sudden results in snowpack tests.
Avalanche Summary
No new avalanches have been reported or observed at this time (5PM Friday). At Treeline on Thursday, shooting cracking from ski tips were observed in very hard Wind Slab, 15cm deep.
Confidence
Forecast snowfall amounts are uncertain
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.
Deep Persistent Slabs
Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.
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.